The man hug: This type of hug comes in many forms. The approach shows just how much affection he's willing to offer.
The pat: Some men lean in with their left arm around your shoulder while their right pats your upper back three times. Too many pats could mean he's signaling you for some foreplay. Too few means he'd rather be hugging his sister. As opposed to the full body hug, all lower man parts stay a respectful foot away, possibly to hide an awkward boner. In either case, if he gives you the shoulder pat, his performance in bed is probably just as tame.
The full body: This hug, involving the body touching from chest to knee, is a clear sign of genuine affection. Typically this isn't left for a quick hello or good-bye hug, but when some type of feelings (love, lust, or like) are involved. Whether you want it or not, anticipate more body contact from this person in the near future.