There are a couple of schools of thought on this. I, personally, opt for a whey shake about 15 minutes after I put down the iron on my last set and then do a whole food meal (complex carbs and protein) about an hour after that. I also train in the early evening, though, so I taper carbs during the day during and while I cut (which I currently am), I take in the largest amount of carbs at breakfast and pre-workout (post I get about 40g or so).
One thought is that consuming carbohydrates immediately after workout halts fat-loss and can blunt GH levels.
The other thought, is to take in carbs immediately post workout (specifically simple carbs) to spike insulin levels and shuttle nutrients into the muscles.
This is one of those subjects that has been debated for as long as I've been doing research on nutrition. My advice: try one method for a week with no other changes (in training, supplementation or diet) and then try the other - compare results.