You can give reputation to a member if you feel that you can give esteem to him/her. Do not abuse the rep system and the Thanks buttons! Remember, generally, members with high rep are respected by the community.
Conditions for Giving Positive Rep
1. If you are very happy about a member's post (especially a map/resource post).
2. If you feel that a member's post is truly very informative.
3. Positive rep should not be given to reward jokes, and meaningless posts.
4. If you are very happy about your own outcome of a tutorial posted in the forum
Conditions for Giving Negative Rep
1. If you are very disappointed about a member's post that broke one of the forum rules (except posting in the wrong section and/or violating Site-Wide rules a, b, c, e, l, o, and p).
2. Negative rep should not be given to reward announcements, stickies, and map/resource/GFX showcase topics.
Conditions for Giving Thanks
1. If you are very happy and thankful about the completion of your request or solving your problem posted in the Need Help? Post Here! section
2. Posts that violated any of the Forum Rules should not be Thanked