Another great thing about Garter Stitch is that you don't have to do anything fancy to shape it. In fact, most increases and decreases pretty much disappear into the bumpy fabric, so it almost doesn't matter what increase or decrease method you use.
For that reason, I pretty much always use knit in the front and back as my increase and knit 2 together as my decrease when I'm working Garter Stitch. If I want to get really fancy and mirror my decreases, I'll throw in a slip slip knit. But most of the time I don't worry about it too much.
What about you? Have a favorite increase or decrease for Garter? I'd love to hear your thoughts.