I like to absorb everything and then let it settle. I read everything in the build threads as we go along. Then skim the finished threads.
Then I choose which bikes I like at the last second in a blind panic because I nearly forgot to vote again!
So basically, it's a combination of the finished photo, and how much the builder has managed to make their build stand out over the months. Honestly, the threads make a difference; for example, Carl's writings earn him points. I'm not exactly sure what kind of bike he'll bring, but the prose woven into his thread have me hooked!
Another way to earn my favor is through audience interactions, especially with Matti. If you took the advice of the hive mind, and it made a better bike, that makes me happy. If you took my advice, it makes me feel like I'm voting for "my" bike.