When a guy is happy with how things are going, he'll often make this sign of approval without realizing it. For example, he may rest his hand on the table with his thumb and index fingers touching if he is enjoying your night together.
Touching fingertips to fingertips is a hint he's feeling cocky, so it'll be tough to get him to listen to you. If there's space between his hands, he's confident but also eager to get your opinion.
A dude will unknowingly use his middle finger--think scratching his face with it--when he's upset. Instead of taking offense, ask him a leading question, such as, "I might be wrong here, but are you unhappy about something?"
Even if your guy hasn't dropped those three little words yet, his fingers might have. When a man feels a strong connection, he'll subconsciously create the love sign-language gesture--extending the thumb, index finger, and little finger--while doing random things.
Sources: Body language and detection expert Janine Driver; body language consultant Jan Hargrave, author of Let Me See Your Body Talk