I really like this guy, but I'm not sure if he likes me. What are signs I could look for?

When you let him know you're interested in doing something with him when he's free sometime, and says, "Great idea"... that would be a hint.

Some guys go out of there way to talk to you.. such as you work on opposite floors and he finds his way "passing by" he may linger and fiddle with things.
Things like that

How old is he/you?:confused: