For me, I had a pretty good idea of what I wanted well before I went. I think it's good to decide the most important things by what you want to get outta the guitar. I actually wrote up 2 different builds. One that had everything I wanted and one that had everything I needed...the no compromise items. For me that was a double cut body that was SC thickness. I wasn't looking to experiment much for tone woods because I wasn't looking for anything way out of the norm. I knew I wanted a Brazilian board cause I love the feel and tone, was just s matter of finding a cool one. There's a ton of options but honestly, I kinda felt the woods picked me. I looked a a pile of tops. I had it narrowed to 3-4 pretty quick. I knew what color I wanted so I asked Paul Miles which would be best for the color and he then rated them 1,2,3... for my color. I took a little time, but they were all great so I went with his #1. The neck I just picked up a bunch and knocked on em. I picked the one that had the longest ring. The back was toughest for me. I didn't intend picking a back that was figured mostly because I didn't want an up charge there. There's a ton of nice ribbon hog back that even have some figuring. But the quilted hog I got was really dense and I felt I'd be making a mistake and wondering about it forever. I figured(no pun intended) the denseness would add to what it wanted tonally.
Are you going out there or having the dealer go?