Try and get the lowest BIN of a player and put him for an average BIN for him, if you do this multiple times you can make a decent profit of a few thousand coins
However, it's difficult as people always undercut...

What do you mean by undercut?
Is that trading quite risky?

In the short term, it's not very risky. However, in the long term it can be due to players rising and falling in price. You're best of buying the cheapest BIN on the market and selling the card on for a few hundred more. It's slow and takes time but you can make some good money from it if you stick at it

1. Simply choose a DESIRABLE player, find his lowest BIN price try get the player cheap(ish) & with a decent profit point to be made, list the card for the same as the lowest BIN, if there are 15+ cards at the lowest BIN price simply list for 250 coins cheaper, it will sell 100% (Works well with IF's with prices 20k+.

2. Find a DESIRABLE ST with 70+ passing, check the price of the cheapest BIN for that player at CAM if the price is 2.3k more than the ST (usually get the card cheaper than the BIN on open BID), you can convert the ST down to a CAM for 900-1k coins, List the card slightly under the lowest BIN at CAM, can make 1-4k profit off every card listed. Be careful not to list too many at once though batches of about 2-4 cards per list cycle normally works the best.