You'll get some points every time you make a meme, submit a meme, write a comment, or (for now) upvote other's people's memes/comments.
But you get a lot more points when people upvote your memes or your comments. You can't really control whether or not people upvote you or not, but I've found that if I make funny meme comments on front page memes, people seem to like that - so that's probably the best advice I can give you. You'll be able to make meme comments once you pass 1000 points.