This isn't so much a post asking for the answer to the question. It's more a post to highlight the fact that you can do this and more importantly that you should (when it's been earned).
If someone posts something that helps you, or simply a post that you think is worthy of a +rep boost then you should +rep them. It'll make them feel better, add weight to their future posts (high REP = respected past comments)
Similarly if someone posts something bad you have the right to -rep them too. This shouldn't really be used if you simply disagree with their point of view/opinion - it should be used when they've done something really deserving of a -rep!
When you + or - rep someone you can also leave a comment for them to read - it's a nice gesture to let them know WHY you've + or - rep'd them.
So... HOW do you +/- rep someone?
On every single post on the forums at the top right you will see a little green icon (see attached example):-
1. Click the green icon (highlighted by the red outline in my example)
2. Select either "I approve" (+) or "I disapprove" (-)
3. Enter a comment if you want to
4. Click "Add to Reputation"
This function is available, can't help thinking it doesn't get used enough - i always try to remember to +rep people when I see a quality post. I am very careful in using -rep and try to only give these out when the post really deserves it.
Anyway - hope this helps you out. I always refer to people's reputation as it generally gives a pretty good indication as to how experienced they are.
Note: +rep's are weighted (at least they used to be!), senior members give more that noobs and +/- rep from PS3NEWS can make or break you! lol