Post-workout nutrition is important to help the body recover from intense exercise (especially weight training). It is not necessary to eat immediately after your workout (if you want to eat immediately after a workout, YOU DIDN'T WORKOUT VERY HARD)! There is a 45 minute to 1 hour window where replenishing your body's fuel (carbs, protein, fats) will optimize your tissue's repair and growth. Carbohydrates are important for glycogen stores recovery. The type of carbohydrates consumed are not as important as the amount consumed (replenishment is the key issue). If you miss this "window of opportunity" to optimize muscle repair and growth, it is gone forever.
So, how many daily carbs should you consume to replenish glycogen stores? It depends on your size and how intense you exercise. Your body needs a minimum of 200 grams of carbs per day if you are a light exerciser. You will feel tired and listless without this amount of carbs.
If your workouts involve plyometrics , speed and weight training, you need about 2.5 grams of daily carbs per pound of body weight. A 180 pound person would need at least 450 grams of carbs each day to function properly.
When you are training for marathons or triathlons, you need high amounts of daily carbs. About 3.5 to 4.5 grams per pound of body weight is needed. So, a 180 pound person would need 630 to 810 grams of carbs per day. These people sometimes use carbohydrate loading before events.
Protein is another critical post-exercise nutrient. Protein provides amino acids which are used to repair and rebuild damaged tissues as a result of intense exercise. Protein shakes will work well here.
To summarize, the post-exercise meal should consist of carbohydrates, protein and a small amount of essential fats. A drink, such as a smoothie, is good because it is quickly digestible. A ratio of 2g carbs/1g protein is desirable. The carbs should be high glycemic , the proteins should be easily digestible (whey, egg or casein) and the fats should be from sources such as fish or flax oil.