1. Put down the tar paper, or some other kind of underlayment.
I used left overs in the garage from building my dad's big house which turned out to be 90% sticky, special stuff similar to Grace Ice and Water Shield, and 10% #30 roofing felt.
2. Attach drip edge.
I used galvanized L flashing that was 1.5" x 1.5" and attached it with roofing nails to every part of the roof that water would run off of. Nailing a strip of 10ft. flashing sounds easy enough, right? Well John and I had a heck of a time keeping it from bubbling, kinking, and just keeping it straight in general. Tis the nature of thin metal, so be prepared.
3. Put the tin on.
This part isn't to terribly complicated. It's easy and goes by pretty fast. That being said, it still took longer than I thought because it's tough to work on a slippery, 45º pitch. It's kinda a two person job. Make sure you have foam closure strips for the ends of the roof so bugs don't get in there. Also make sure you have something to cut the tin with. I ended up using a grinder with a cutoff wheel and that worked really well.
4. Ridge Cap
Instead of using the dedicated ridge cap Home Depot sells, I ended up using two pieces of 4"x4" flashing, just like the drip edge only larger. It was a lot cheaper and had the look I was going for.
And that's it. If you're looking for more techenical information, like exactly what kind of screws or metal roofing I used, you can check out my spreadsheet under the Budgeting Resources page.