re set stats?

I heard a few people talking about this, and i was wondering how and if u can do this? cuase i didnt really know wat i wanted to do and now im at 22 with melee stats using rifles.....

 so yhea if its possible to reset stats.. how pls? =)

thnx =)

oh forgot to ask, can u do this as many times as u want? ot just once?