I work in a shoe department. Here are some tips:
1. Buy something with arch support, or buy inserts.
2. Don't think that if you try them on and they don't fit right, you can 'break them in'. Leather stretches, but nothing will go from a size 7 to a size 8.
3. You don't need as much extra room as you think. Too much, and you'll wind up with blisters.
4. Those flexible running shoes? Those are for running. They provide no ankle support for walking and not a lot of protection for the bottom of your foot. If you have any sort of back, joint, or foot pain, avoid these.
5. Sweaty feet? Be careful of the UGG style or anything with fur or wool lining.
6. Be aware that a lot of hiking boots that are on sale right now have winter lining. Make sure you can remove it.
7. You often get what you pay for when it comes to lasting quality. However, you can find some really comfy shoes at great deals! They just fall apart after a few months (which is no problem if they are only for BM).
8. Don't wear fancy-pretty shoes and complain about your feet hurting. It will make everyone resent you.
9. Wear your shoes/boots around a couple months before introducing them to the Playa. That way, you'll know how they feel after a 16 hour day.
10. Buy comfy shoes/boots and dress them up! Their are lots of websites that teach you how to mod you clothes. Google it!