First, don't sweat never having had a girlfriend. There's nothing wrong with being single, and anything else is a cultural norm that has very little real basis. (Some, but you're not asking.)
Second, the essential trick to having (and keeping) a girlfriend (read: "successfully loving someone else") is to find it completely unnecessary (read: "My life is good and worthwhile regardless of whether or not I'm in a relationship.") The traditional, and far more succinct, advice is "Love yourself first." If not having a girlfriend is becoming a problem for you, then you need to look at yourself and improve yourself such that it isn't. Being needy isn't attractive.
Third, Steve's comment can be likened to Gandhi's "Be the change you want to see." You've correctly understood that what you need is to be a good boyfriend.
The essence of being a good boyfriend is stripping away the "boy" part. Be a good friend. In fact, be a
great friend. Treat all women (and men, for that matter) well. Listen. Help people in need. Encourage the uncertain. Be honest and forthright.
Somewhere along the line of being this great person, you'll meet a girl who's awesome and interesting and beautiful. And being the honest guy you are, you tell her. She'll be flattered; you'll talk; there will be dinner, movies, and long walks on sidewalks (since we're paving over them beaches); next thing you know, you'll be chatting about whether or not you want to spend the rest of your life together. Or not. Who knows?
It's all very mystical. But it starts with you, yourself, and being awesome.
Angela recently wrote a post on this subject here:
The Crocodile Nun - a long article about romantic love
It's worth a read-through; she says a bit more than I do here.