There could be plenty of reasons why a guy doesn't want a girlfriend right now. He could have just got out of a bad break-up and is still trying to work through the emotional after-effects. Or he could just like his single state. If you want to undertake the challenge of getting such a reluctant guy to go out with you, you can succeed if you have a bit of savvy.
Be his friend right off of the bat. Immediately ditch the idea that he's someone you will conquer and instead focus on really getting to know him. Invite him to group activities and keep every encounter you have with him super simple.
Respectfully inquire about his "story". If he's said he doesn't want a girlfriend, some part of you has to know you should respect his wishes. However a little light aggression will get you closer to learning if it's his defence mechanisms kicking in and he's just sworn off girls for a long time or if he really needs some down time to get himself back on track. As you begin hanging out with him, casually start talking about his single status and see if he's willing to divulge information.
Do plenty of things he likes to do. From hanging out at the sports bar to volunteering to make him a bagged lunch for his fishing trip, put yourself in as many situations with him as he will allow.
Host your own event to get him to see how things operate in your world. If all of your friends with him aren't mutual, give him a glimpse into your life by inviting him over for game night with you and your pals. Be sure the event isn't a couples thing so he doesn't feel obligated or awkward about being your guest.
Ask him out for a date. Guys notoriously have a lot of pressure to initiate dates. Even as women become more and more empowered, the great majority still are waiting for guys to do the asking. Switch the tables on him by being confidently blunt and ask him if he wants to go out. Keep the first outing casual so that he's doesn't feel pressure. The first sign of him back in the dating pool might scratch up emotions from an old relationship that turned out badly. Make plans to go somewhere he wants to since you asked. If the majority of your attempts to get close to him have been successful, you should be well on your way to getting him to ask you out on his own.