I've been getting lots of questions about the best strategy for the free $500/1 hour bonuses listed a few posts back. There are two viable ways to play there, and a few things to keep in mind.
You can only transfer a maximum of $200 in winnings from the free money into your real account, so keep that in mind. Play any game during the free hour and remember that your goal is to run your balance up to $700, as at that point you've hit the maximum you can transfer over to your real account, which is $200.
Because of the high wagering requirement for the bonus, if you just grind out the WR at blackjack on autoplay, you're likely to lose your bonus, plus your deposit (which is either $20 or $50, depending on which casino you play).
If your goal is to grind out as much of a profit as you can, with a minimum of risk, your best shot is to play French Roulette, and make even money bets. Bet the minimum and grind it out on autoplay. The HA of French Roulette at Microgaming casinos is 1.35%, and wagering at that games counts 50% towards the WR.
So if you transferred over $200 in winnings from the free hour, your WR would be $12,000 at French Roulette, and your EV would look like this:
EV = $200 (.0135*12,000)
EV = $38
The other way to play these is to be more aggressive and to try to build your bankroll up first by making large wagers at BJ, either running up your bankroll or busting out. Since you only deposit $20 or $50 of your own money, and start with either $220 or $250, you don't have a lot of capital at risk, and have a chance for a fairly big payoff, if you're willing to bust out.
In this scenario, you'd set a target to shoot for, betting something like $50/hand at blackjack. Say it's $450, and that you hit a nice run and run your bankroll up to 4400. Then you revert back to grindy mode, and grind out the rest of the WR at French Roulette, as outlined above. The difference, obviously, is that you're effectively starting with a bonus of $400 in this scenario, so your EV is $200 more, or $238.
The downside is that you'll bust a lot betting aggressively, and will be out your deposit of $20 or $50. Which sucks, but that's gambling. You can also be more aggressive with yur target, shooting for a bigger score, but that also increases your likelihood of busting out. Again, that whole gambling thing.
In the end, these are nice bonuses, especially when offered at three different casinos. It's not quite as easy, dead money as you'll find with some of the cashable signup bonuses, but there's a lot of upside with these, with a very small initial outlay of money to take a shot at them.