You don't really drain lactctic acid from your legs. I don't exactly remember how, but lactic acid can be run through the citric acid cycle once the muscles in your legs have enough oxygen to do so. (The reason that your cells produce lactic acid in the first place is because your cells need more oxygen than they're getting, so in order to make quick atp, they skip the whole aerobic respiration part and get atp through lactic acid fermentation)
I'm big into distance running, and I find that the best way to get that burning sensation out of your legs from the build up of lactic acid is to just slow down the pace and let things work themselves out. Cramps, however, are not caused by build up of lactic acid as much as a few other things. The major culprit there is either an imbalance of sodium and potassium (usually less sodium) or dehydration. To get rid of cramps, eat foods rich in potassium through the day and drink something like half water and half gatorade while you work out. You can even just put some salt in your water(just make sure you don't have too much to drink at once, because then you'll get those side cramps or side stiches.) However you do it, just make sure that your body is getting a good balance of water and sodium before, during, and after a workout.
Also, if your legs are sore the next day, its good to stretch them and go for a short, easy run. The running will usually work out problems as long as you don't do too much.