Ah, love. Or should I say "like"? It's always tricky to see what to do if you think a guy likes you. Overstep the boundaries, and you risk awkwardness. Don't do enough, and he's gone, or stuck as friends. Here's how you can determine if he likes you as more than a friend if he doesn't say so directly.
He acts differently around you compared to other people
This is a pretty good general rule to stand by. It doesn't necessarily mean that he's extra nice or flirtatious around you, since he could be hiding his feelings for fear of rejection or because he doesn't want people to know. He just acts differently around you, maybe in his body language, gestures, what he says, or tone of voice. Of course, there could be other reasons, such as him thinking that you act strangely.
He wants to talk to you
If he's constantly thinking about you, then he'll want to talk to you. This is his way of seeing how you feel and if you feel the same way. This can also include other forms of communication than just face-to-face. Maybe it's through text messages, email or facebook messaging. By chatting to you through these communication channels, it's easy for him to avoid potential awkwardness but also get to know you more at the same time. If he wants to talk to you one-on-one, this is a possible sign that he likes you. If he wants to talk to you for hours and tries very hard to keep the conversation going, this is a surefire sign that he likes you.
The way his friends act
If you and he belong in the same circle of friends, it's possible that some of his closer buddies might know about how he feels. Armed with this knowledge, they might find it funny and endearing and thus, act extra happy or giddish around you. On the other hand, they might drop hints when you speak with them or joke amongst themselves.
On the other hand, if you don't know his circle of friends, maybe they know you. If they do know you, then it's obviously because he's been talking about you to them. However, just because his friends don't know you or act normally around you doesn't indicate otherwise, since he might just keep to himself.
He doesn't mention other females
Guys like to talk to other guys about other females. They'll even be comfortable sharing their thoughts with their female friends. If you're just a friend, then he'll be open to giving his opinion about what he thinks of other women. If he's interested, though, he won't make such remarks about other women since you might think he's not interested in you.
Physical and Eye Contact
If he likes you, he might like to do things such as lightly touch your arm, "accidentally" brush against you, or give you a nice hug. Of course, some guys are shyer than others, so they might refrain from doing any physical contact whatsoever. But it's natural if a guy's interested that he'll want to be closer than normal. He might want to sit beside you or closer to you. Eye contact is a give-away if he ends up looking at you for a long time. If you're looking away, he might sneak a glance at you. And then there's "the look", where your eyes lock and everything else fades for a moment. This is a dead give-away.
Spending time alone with you
Of course, two people can spend time alone and still just be friends. But if he suddenly wants to spend time with just you, and it becomes more frequent, there's a pretty good chance that he likes you in a romantic way. He might cover it up somehow if he's shy, such as saying that he wants you to come "check out an event" happening on the weekend.
Or, both of you are hanging out in a group, he'll start talking to you and both of you will end up being split off from the rest of the group because both are you are engrossed in your conversation, or because it's his subtle way of saying that he's paying attention to you.
A Closing Note
Some guys are more subtle than others when it comes to expressing their feelings. Some might try to avoid expressing it at all. See how he acts and decide accordingly. If you have a feeling he likes you but isn't making a move, you can suggest going to events or doing things together to get to know each other better. Be careful, though, that he isn't leading you on or has other motives, such as leading you on for his own amusement. If he seems like a nice, genuine guy, go and make the leap!