1. Ask them unrelated questions, as they will probably open up as time passes further on.
2. Ask them out (risky).
3. Get close to them, and eventually you two will become close friends. Then, open up to them.
Try entering a convo with him.
As things progress further and further, begin to ask him out ***slowly***.
Or, I don't know?
Not the best for this type of help.
Help, I know it's a lot to ask, but I need your help: how do I get over someone? I'm in love with a guy who's really nice and sweet, but he's straight, I don't know how to fight this feeling.