i play pretty regularly and have been playing for a while, and one of my friends wanted to get into it...so i took him with me whenever i went and you basically have to play against good people who are serious about playing(e.g. no one wearing flip-flops). So just go down to a park where people play and just try to get the hang of it. And its a pretty complex game, so try to understand the little things that some of the better players do and try to replicate it. So , as long as you keep playing, i think you'll keep improving.
oh and play on your strengths...if you're well built, go to work down low in the post....or if you're quick, try to ask for the ball and create a shot for yourself...basically if you find one thing you're good at, people will focus on that which will open up other things for you. like if you're quick and you can take people of the dribble, they'll play you loose, which can then give you more open shots...etc.
and defense...as long as you play good d, people will want you on their team.