Second account method
This method involves the use of a second account, however dont worry if you are an Xbox 360 user, you still dont have to pay for another account as only a silver membership is needed (which is free)
To make this simpler, I will call:
Your main account, the account which you play on and want all your coins on, account A
Your second account, the one which you are using to complete this method, account B
Seeing how you probably dont have 2 xboxs or PS3s to save you the hassle and time of signing in and out of each account to do the transactions it would be much easier and quicker for you to use the web app for account A, which can be found at ea.com/soccer/fifa-ultimate-team/app
The web app allows you to trade players easily, which is all you need to do on account A,
first of all on this web app, you need to get any card you dont want anymore, then put it up for a price that will be easy to find later, as an example I usually put my useless card up for 1800 bid and 1900 buy now, therefore it is much easier to find in the auctions when needed, saving you time, time is money.

On account B, you need to go to ultimate team on your console and start a new team (this is possible for Xbox 360 users to do with only a silver account (you only need a gold account to play online) after starting a new team you will get a team full of bronze players, first of all you need to go to one of the players and press apply item, send the available item to your trade pile, whether its a contract or a fitness card or whatever, just so you can do a trade offer later. Now you need to discard every player you received, after you have done this you should have at least 450 coins on account B, now you need to go to search auction, and search for the original card you put up for sale on account A, trade offer this card with the card you put in your trade pile and all the coins you have, then simply switch over to account A on the web app, accept the offer and now you have all new your coins, put the new card you just got up for sale again so you can repeat what youve just done. Now on account B you can delete your team, meaning you can make a new team, getting a whole new squad of bronze players and therefore being able to rinse and repeat this process.
A quick summary of this method:
Make a new team
Discard all the players
Trade offer yourself the coins

Although it sounds like a lengthy process due to my description it only takes a few minutes each go and is completely risk free, you are guaranteed to make around 500 coins every time.
Bronze Pack Method.

This is a hugely popular method where you purchase bronze packs then resell the contents for profit. Each pack gives you 2-4 players (sell for 200 each), kits & balls (200 each), and contracts & managers (150 to 300 each). The main problem with this method is that you need to sell these cards to make any money. Since bronze cards have the least value, and also the least interest, you may experience days without selling and of the cards, however if everything does sells, which it will eventually, you should have made 5x the cost of the bronze pack.
As you have probably worked out this method gets you very little profit, and can be painfully slow, which is why I only recommend it to people who have very little to no coins, to be honest I dont really understand why it is so popular in the first place.

Some people think that buying gold packs is a good way to make coins, theoretically speaking it does have a massive profit potential, for example if you pull out an inform Ronaldo or Messi you have just made over 1million coins. However, from my experience of playing ultimate team since 2009, buying gold packs is usually a waste of coins, when buying a gold pack it is rare that you make your coins back let alone a profit. Whether or not thats just my luck or not, I dont know, but I believe the coins could be better used elsewhere to generate guaranteed profit.
Discard Method
The discard method is a very easy concept and simple to do, there is no risk however the profit returns are not as big for the time you put in compared to the other methods, unless you get lucky.
First of all you need to search for gold players on the auction, put your maximum bid on the search at 300 coins, now you need to bid on every 75+ overall gold player that has a bid under 300, making sure that you dont bid more than 300, as then you may be making a loss. You can also search for a maximum buy now of 300 coins, the cheaper you get the player the better, however there is sometimes competition and it can be hard to get the player much cheaper, after you have won the auction you need to discard the player, which is where your profit comes from.

The amount of coins you get from discarding a player is based on his overall rating:
You get 300coins for a 75 normal gold player, and then an extra 4 coins for each player rating above 75
You get 600coins for a 75 rare gold player (shiny), and then an extra 8 coins for each player rating above 75
For example, discarding a 78 rated rare gold player will give you 624 coins (600 + 3*8)
Youd be surprised at how lucky you can get with this method, I have got lucky quite a lot of times and found highly rated players up for a buy now of 200, the only reason I can think people would even put their players up for this price is because they are either quitting, or trying to really annoy there friends.

Contract Method My Favourite
The idea of the contract method is to buy contracts low (usually at off-peek times) and then sell them high (at peek times).
Peek times are usually at night time, when people have got back from work/school and have time to play on Fifa.
Off Peek times are through the day, when the majority of the public are busy, or very early in the morning when everyone is still sleeping.
So the strategy I use at the minute, because contracts are so expensive at the moment, I buy as many as I can for 250 and cheaper, using buy now searches, and then when I know they are going for more money, I put them up for sale with a starting price of 600 and a buy now of 650 coins. As you can see you are getting more than double your coins, and all youve done is buy something and re-list it later in the day, easy right?
Contracts can sell for more however putting them up for sale at this price gives a much greater chance of actually achieving a sale, the faster you sell these contracts the faster you can list more and therefore sell more.
The more money you have to start with the greater you can do this, as at some points I was stocking up to 80 contracts a time (theoretically the maximum, with 50 in your consumables and 30 in your trade pile) before I would sell them, and if I was making the minimum of 350 coins per contract, that would add up to a profit of 28,000 coins for just one load of contracts, and that was just my minimum profit, bearing in mind you can sometimes get the contracts as cheap as 200 coins if your quick and lucky enough, and sell them for more if the market is good at the time.
Using this method you can at least double your coins within an hour, and its very simply with close to no risk, which is why it is my favourite method. I realise trying to buy the contracts so cheap can be time consuming and very tedious as there is not always many for sale, so at times like these when the market is inflated you may have to pay more, however you will always be able to make a profit buying and selling contracts
Buy, Boost, Bank

This is a fairly underused method to generate more profit from an otherwise lower value card. This method involves buying the player cheap, in an unpopular formation, and then applying cards to him to boost his profit potential.

For example:

We buy Walcott for Arsenal, who is currently and always will be a very in demand due to his pace, which makes him a great player to choose.
Buy the player in an unwanted formation and position combination such as a RW player in 4-3-2-1 formation with a 7 match contract left on the open market for 13k (these players are cheaper as they are not what people are looking for as the formation 4-3-2-1 does not have a RW position). We could resell the player immediately for 15k and get a small 2k profit. But with Buy, Boost, Bank, we increase the value of the card by:
Changing the formation to 4-3-3
Adding Player Attributes increase to highlight the card
Adding a 28 contract
Then Setting the auction for 20k BIN.
Do you see how that can make such a profit? Now a buyer can use this card immediately in his 4-3-3 formation without worrying about contracts or chemistry. The Player attributes also generates extra attention since the rating increase causes the card to get highlighted in the listing, meaning it stand out.

The Expert Trader

This method works really well when you find out which players sell the best.

1. Search auction for gold players at a minimum buy now of 5k
2. See what is selling the best and create a list of 10 to 15 players, finding out what is a good price for each player
3. Search for these players at the lowest BIN price
4. Once you have bought the card re sell it at a higher price
5. Rinse and Repeat
Just like the contract method, you can usually get these players cheaper at off peak times, however the difference is youre targeting a small group of players which you know the best prices you can get for them. Using this method occasionally makes you stumble across much better players at a bargain price, which is just another benefit.

You will eventually get good at recognizing deals in the marketplace, you will know the value of players and when a player is cheap so that you can make a profit on them, making you an expert trader. This method can also be used on other types of cards, such as formation cards, which I also trade a lot of.

Pump and Dump This is how I made my million coins, I controlled the market for one player.

This strategy is not for the faint hearted, it comes with big risk, but with that risk comes massive profit potential. To do this strategy you really need quite a large amount of coins to begin with. Have you ever been searching for a player and seen multiple versions of that player all sold by the same person and wondered whats going on? No its not the imaginary duplication glitches, this is why.
This method involves pin pointing 1 individual player; the idea is to buy as many of that player as possible, which in result creates a short supply in the market place. This increases the price of that player to your benefit; it is simple supply and demand. Once the demand is there, now is your time to make your money, you can unload your cards at a higher price as the demand is there .

Example


We buy every Darren Bent on the market for under 5k, now the market has a low supply and the current Value of Bent has therefore increased, now you unload all your cards back onto the trade market at say 8k buy it now, you dont want to put the price too high because this current increase it the players value is only temporary until people start to undercut you again and the price comes down, so you want to sell your players while you can.

As I said this method is very risky, this is due to the fact that however unlikely it is, other people may put the same player up for sale just after you, at a cheaper price and then you are stuck with all your cards. However even if that happens, you will usually get your money back, and if it works? Massive profit returns..
3,000 coins per player isnt the biggest return per a player you can get, however even just at the price, if for instance you bought and sold 20 of that player, thats 60,000 coins in one hour.

Thanks to "Vid"
Hope I have helped