I try to answer as many questions as I can, and when I am not doing that, I am going to the 'review' section and doing what I can there and when that is done, I read through as many questions as possible (flagging if necessary, commenting as necessary) - is there anything else I can do to help?
If you have time to waste, you may want to read this guide I wrote to helping moderate the site.
However, if you already are commenting/flagging things and going to /review, then you probably have that covered.
You may want to try editing posts to improve grammar/formatting as well (I think you already do this too)
I guess the best thing to do is look for more questions to answer (or ask some good ones yourself!). Sometimes, scouring through the back end unanswered section sorted by votes helps; there are many good questions that got neglected by accident there in the later pages.
You're also welcome to participate in chat. This doesn't help the site, but it's fun :)