The mechanics and amounts of loyalty bonuses run the gamut from casino to casino, but the basic engineering at all casinos is the same; for every amount wagered at the casino they will return a percentage back to you. That said, some casinos definitely reward loyal players more than others with their loyalty bonus programs.
Lincoln Casino for example, all have a very user friendly loyalty bonus; you can earn an extra 5%, up to a maximum of $150 per month free where the bonus is added to your deposit automatically.
Loyalty bonus may be based on the game play. Liberty Slots Casino before announcing new Six Shooter Bonus used to base loyalty bonus on amount of time one played the same game, like Queen of The Nile Slot Machine or Reel Deal slot machine.