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A 'perk' is basically a character class. There are 10 perks to choose from, each with its own abilities. Select a perk that suits your playstyle, but remember you can always change it if you want something different.

Note that you will receive all XP earned in a match whether you kill the boss or not, no matter the difficulty or length. But, if you quit out of a match for any reason, all XP gained is lost.

There are five achievements for leveling up your character. With each level gained, it takes more XP to get to the next level. While playing solo on Normal difficulty might seem to give you more XP for your buck, it's probably better if you play with a group of people as the number of Zeds is increased with more players and you receive XP whether you just shoot the Zed or kill it.

There are only a couple of ways to earn XP in this game; killing/injuring Zeds and healing your teammates. Plus, the XP payout is minimal, so this is probably going to be a grind after you've unlocked all the other achievements. Occasionally there are double XP days or weekends, but they are often not announced.

Each perk has specific weapons that you can use if you want to level up that perk. If you select a weapon that is not designated for that perk, you will level up the perk it is assigned to. Note that some weapons are for multiple perks. For instance, the HMTech-401 Assault Rifle is a multi-perk weapon. Getting kills with it counts towards the Commando perk while the secondary mode of a heal beam levels up the Field Medic perk. If you are dedicated to leveling up a specific perk, make sure you select weapons for it.

In addition, there is a snap aim feature when you press [ Register or Signin to view external links. ] . This is helpful when you are up against a group of Zeds as you can quickly alternate pressing [ Register or Signin to view external links. ] to aim, [ Register or Signin to view external links. ] to shoot, [ Register or Signin to view external links. ] to aim, and so on. This guarantees a lot of assists for which you receive the same XP as when the Zed is finally killed.

It is recommended that as you increase your level, you play more difficult matches. Higher difficulties have even more Zeds with slightly higher XP values, so you receive more XP per match, but they take more damage to kill them. Be warned, if you increase your difficulty prematurely (before reaching Level 12-15), you might not survive to kill the boss. If you are going to play a match on a higher difficulty, playing with a team is recommended.