Simple. Rate the above users signature. Give them a review and a score out of 10.
Rules! (courtesy of your resident friendly MoD)
1. DO NOT BACK TO BACK POST. Wait for 3 or 4 sigs to go by until you rate again.
2. DON'T RATE AN AVATAR/SIG THAT YOU'VE ALREADY RATED unless it has gone through a significant change.
3. WHEN YOU RATE AN AVATAR/SIG, you must provide some context to their score. Don't just say "Nice! 10/10. Rate mine now." It shows that you don't care about anything except making people rate yours for free. It's also completely unfair.
That'll do. Have fun rating!
~MoD