If you dont have anything to share, then getting points is going to be slow and painful for people. As said before, posting and making threads is the best way to increase the level, but it's going to take a lot of time. I've researched a bit so I'll try to restate some things.
When making threads, talk about popular topics that people might enjoy. Just making random threads wont be approved, and even if they are they might not attract attention.
Dont reply in leaks since it will reduce the level by 5. Dont open a link without a contributor level equal or above 10. It wont hurt at first, but it wont paint a good image when people see your account.
Post replies that are actually useful. No idea how this ties in to level, but I feel as if typing in random replies wont boost your level at all.
Reiterating, if you dont have any leaks or things to share, then the last options may take a while. Unless you want to pay, which I'm sure is not many, then be an actual contributor which I know people dont like. Those are just some ways, there may be more I havent covered.