If you're gay how do you ask a guy out?

It is important to ask someone who is also gay. Be careful not to ask out someone who is straight or someone who hasn't come to terms with their sexuality yet. this might cause troubles.

Once you have come across someone who is also gay and perhaps interested in you, ask them like you would ask anyone else. Perhaps ask them on a date or ask them to hang out. Get to know them and go from there.