Do a search. There’s been a gazillion or so posts on this topic…
Here’s a few recent posts:
http://yoyoexpert.com/forums/index.php/topic,81705.0.html
http://yoyoexpert.com/forums/index.php/topic,84867.0.html
http://yoyoexpert.com/forums/index.php/topic,84867.0.html
http://yoyoexpert.com/forums/index.php/topic,92072.0.html
http://yoyoexpert.com/forums/index.php/topic,95371.0.html