There is a variety of ways a player can receive casino comps. First is the new player bonus which the online casino gives the player to sign up for a real account. This is anywhere from a no purchase comp to a deposit bonus.
Second when you purchase and play at any casino more than a couple times the online casino will send out special offers on your next purchase. Some might even give you free cash comps as a extra bonus.
Third is the loyal player casino comps. Some casinos have a built in system to earn comp points and also give loyal players extra bonus throughout the term of playing at the casino. This is a appreciation bonus. So always make sure you give the online casino a legit email you will check often to claim these extra comp rewards.