Fortunately, a few very gracious people are out there to help people like me!
The Purl Bee posted this great photo tutorial on weaving in ends in all sorts of different ways, so you can find which is best for your project:
|The Duplicate Stitch Way|
And Sandi Rosner of Twist Collective seems to have written this article on seams directly for me. I'll definitely have it close at hand once I go to sew up my next non-seamless garment (which might not be for a while, but she's made me brave!).