I think, in every time that you vote, post or comment on a question, your points will be increased. The team of SRF and admins can give more explanation pertaining this issue.
The points are calculated through the voting system, everytime someone votes up/down on your question or an answer you gain/loose points depending on the vote. The reputation is calucated based on the number of points you have.
This document has more details on the Points/Reputation : http://www.s-rf.org/site/reputations