It could be in the form of a deposit bonus, or a no deposit bonus for that matter, free-of-charge wagers or free spins and lots more besides. There are millions of bookmakers, betting sites and online casinos out there, and the beauty of that is that the absolute vast majority will offer free bet promotions in one form or another.
Ask any expert bettor and they will tell you the same thing: to help build your bankroll, you should be making the most of free bet offers.