I've found that a regular glue stick, like the kind from Pioneer, are the best option for covering pages and the cover of my book. They're inexpensive, easy to find and easy to apply. You'll use a lot of glue—I usually go through about 2 or 3 glue sticks for one sarabook™ so I always have a couple extra on hand.
Whatever adhesive you choose, just make sure it's not a liquid. Liquid adhesives will warp and buckle your paper, which is hard to fix and harder to undo.
When attaching quotes or smaller pieces of paper, I often use my Hermafix—it's a dry adhesive so it will hold the paper without sinking through it.
For dimension, I count on foam mounting tape. I'll attach a quote or word with one layer for a little lift, or use two layers for more height. I love how the embossed paper charms look on foam tape.
When covering pages or cutting any kind of straight line, I really have to use my paper cutter for accuracy. I have the Cutterpede cutter, which I love; you can also use a Fiskars Personal Paper Cutter.
I have to confess: I'm terrible at cutting circles! Then I discovered that my problem wasn't all me—it was me, trying to use regular scissors to cut the circular tags. I have much better luck with short-blade scissors like the Fiskars SoftTouch or the Cutter Bee scissors. Both have a comfortable handle and are made for cutting curves.