I love my Add-A-Quarter ruler. Here's a link to the manufacturer's site with a tutorial. A video would be better, and maybe there is one out there, but this will give you an idea. There's an Add-An-Eighth ruler too. I would go with the 12-inch Add-A-Quarter. The other would be too short for many pieces, but if you can afford both, they are both helpful. I have done PP both with and without this ruler, and the ruler is very helpful.
http://www.addaquarter.com/how_to.php
One more tip I got in a class was to look for the "Post It" tape. The only place I've seen it is at staples. It's like a post it note, only it's in tape form and from a tape dispenser. It allows you to tape ripped foundation paper, and still cut through it. Regular tape doesn't work well with a rotary cutter.