General question about casino bonuses

[Salva135]

Can someone explain to me how to best take advantage of these? I've been doing poker bonuses for a while now, but feel like I'm missing out on a lot of free money by not jumping into the casino whoring as well. My question is, though, is it possible to earn these bonuses without losing a ton? My understanding is that most sites require you to wager some x money times the bonus amount to earn it, but don't you run the risk of losing a lot just playing a bunch of -EV games? Or is the bonus amount usually more than enough to compensate from the small amount you risk earning it? What wagers are the least risky to play? I've heard some say blackjack, but I don't know anything about playing optimal blackjack -- do you have to be an experienced player to do this successfully?