Having watched a number of videos in the past couple weeks, I have heard the pros refer to lots of places as a good spot to three bet. so my questions are:

1. Obviously a loose opener is part of that equation, but what else should I look for when looking for spots to three bet light? 

2. What conditions would make a spot a bad one to three bet light? 

I had been experinmenting with it more, and other than just looking for aggressive openers, I feel like I am just guessing for the most part, so any guidence would be appreciated. 

Thanks.