First Thing in the Morning: The period between when you go to bed and wake up in the morning is the longest that your body goes without food. "Break the Fast" with protein. In addition to providing much needed amino acids for muscle maintenance and rebuilding, proteins provide more stable, sustained energy than that donut or bagel that you're currently chowing on. Opt for a faster acting protein like whey first thing in the morning.
Pre-Workout: By drinking a protein shake about an hour before your workout, you'll "Prime" your body for growth with BCAA's and other essential amino acids. Whey and egg proteins are a good choice, because they are easy to drink and quickly digested.
Post-Workout: The 30-60 minute timeframe following exercise is the single most important time of the day to get protein. Enzymes and hormones are actively repairing and rebuilding exercise-induced damage as well as replenishing glycogen stores, so your muscles are especially receptive to nutrients. By supplying a post-workout recovery protein containing whey, casein, egg, and simple carbohydrates during this "window" of opportunity, you'll help ensure that you're recharged and ready for your next training session.
Between Meals: Consuming a protein shake in between meals not only helps keep muscle synthesis maximized, it also helps keep body fat and body weight in check. Proteins help stimulate the release of gut hormones that trigger a feeling of fullness or satiety. Dairy proteins (whey, casein, and milk) are considered to be better appetite blunters than other protein sources, especially when combined with dietary fiber, so choose a product with one or more of these proteins if weight control is part of your goals.
Before Bed: Prepare your body for the long fast ahead with a casein protein shake a half an hour before bed. Unlike whey which is rapidly broken down in the gut, casein is digested at a much slower rate releasing its amino acid constituents over several hours throughout the night while you sleep. For this reason, casein is commonly referred to as a time-released protein. Casein is also considered anti-catabolic because it's rich in glutamine and other amino acids that help protect against muscle breakdown.