A man falling in love might go out of his way to please the person he's interested in dating. Another sign to look for is whether he loves spending time with that person.
If a man goes the extra mile for someone, then he could be falling for that person. If he wasn't falling for that person, he probably wouldn't put in any extra effort. Additionally, if he spends more time with someone than he does hanging out with his buddies, he might be falling in love. He is also likely to take time off from his own hobbies in order to participate in the other person's hobbies.
The way a guy smiles is often a sign that he may be falling in love. If there is a certain twinkle in his eye, then he might be in love with his suitor. Another sign that a guy is falling in love is if he spends large amounts of time talking to the special someone. Stereotypically, guys generally do not talk things through unless they are with someone they love or feel comfortable around.
One important sign of love is when he allows the person freedom. Love is not about control. If a man tries to control someone, it might be obsession and possessiveness, not love.