Sometimes it's hard to tell whether a guy is interested in you or not. But just because he doesn't want to come up to your apartment after the first date or jump at every opportunity to make a move, it does not mean he's "not that into you." Instead, he could just be shy—and that's where you need to make a move. But you need to know how to tell if a guy is interested in you in the first place.

Most guys will usually accept any form of female attention, but you need to watch for subtle body language clues to figure out if he's just using you as an ego boost, or if he really wants to hear what you have to say.

Look at his facial clues. Does he smile often? The smile can't be a fixed smile, and it should react to what you're saying. He should also be making frequent eye contact instead of shifting his focus elsewhere.

Then evaluate his body language. Does he look relaxed? A guy who doesn't appreciate attention will usually be tense. His legs won't be stretched out, and he won't be sitting back. Some classical signs of tension that a guy exhibits are tapping his foot, bouncing his knee or rubbing his hands together. Don't just wave them off as nervous tics. You are clearly making him uncomfortable.

If his arms are crossed, that is a sure sign that he is not feeling free and open. But it also depends on where his arms are crossed. A more relaxed crossing of the arms lower on the chest—maybe across his stomach—doesn't mean he is feeling threatened or confrontational. Instead, watch for a tight crossing of the arms high across his chest.

Positioning of legs is also important. If his legs are crossed away from you, it shows disinterest. Likewise, if his legs are crossed toward you, he is interested. When stretched out and uncrossed, at least you know he is relaxed and is enjoying your company. It doesn't indicate anything in particular because he could be interested or just enjoying the attention.

Even with all these body signals, the most important part is seeing whether he responds to you at all. If a guy is really shy but still attracted to you, he will still always respond to questions with more than just a one-word answer. If he reacts and responds to your attentions, chances are he is interested.