Despite having a reputation for being more direct about attraction than women, men are still sometimes difficult to read when it comes to determining whether or not they are interested in you. Every man is different, but even if he's not coming right out and confessing his attraction to you, there are certain key things to look for in his actions that will give away his true feelings.
He Calls Frequently
Talking on the phone is not necessarily a common practice for guys, so if he's actually dialling your number on his own initiative on a regular basis, that should tell you something. Unless he's only calling to ask you a favour or get information on something he knows you are privy to, it's reasonable to assume he has interest. It's even more reasonable to assume he has interest when he calls for no reason other than just to talk and see how your day is going.
His Friends Know You
If you are just meeting a friend of his for the first time and he seems to already know everything about you, chances are he's spending quite a bit of his time talking about you. He has little reason to do so unless he likes you, so take this as an encouraging sign. When all of his friends know you prior to a proper introduction, it's practically a sure thing.
He Touches You
Even the most subtle form of physical contact from a guy is a pretty big sign of interest on his part. If he touches you in any way, whether by putting his hand on your arm lightly, patting your back, or playfully grabbing your shoulder, his motivation for doing so is likely fuelled by a developing romantic interest in you. This is especially true if he's finding ways to do it frequently.
His Mind Becomes Blank
The stereotypical stammering, lost-for-words moments guys experience when confronted with the task of charming a woman they are attracted to actually do happen in reality. If your presence seems to make him become strangely forgetful, it's entirely possible that his attraction to you is the reason behind it. When he's focusing intently on his feelings for you or on how he might make a good impression on you, basic short-term memory skills will suffer accordingly, which could explain why he suddenly doesn't know something painfully obvious.