Most Helpful Guy
You might know however it could depend a lot on what type of guy it is. If it's a more socially awkward type of guy (which is perfectly fine not everyone is a casanova) then you might think he is about to kiss you then suddenly doesn't. This might not be because you misread the signs just that he got nervous which happens to the best of us, especially around those we care about. However if it's a more private setting like a movie or walk rather than a public place like a club then some of the basic signs are if he's been looking at your lips (hard to follow and know for certain), if he moves your hair behind your ear, or if he's licked his lips a few times in the last few minutes to ensure they aren't dried out.
Most Helpful Girl
It's as simple as this
If you can tell he glances at your lip when you talk (if he doesn't have the habit of avoiding eye contact), or he looks at your lip and your eye then your lip. Sometimes he ll compliment how pretty/hot you are first