Marinate for at least 3 hours, up to overnight.
Before cooking, if you have time, take it out of the fridge, spread it out on a sheet pan or something similar, and let it come up to room temp. (This should take 30 to 45 minutes, depending on the weather.)
Bringing meat up to room temp before you cook it ensures a better sear, so more juices stay in rather than run or steam out.
If you're grilling on coals, this is a good time to get your coals started.