Pick somewhere you don't mind being stuck at. If the industry tanks and your seniority position freezes for a year, will it be doable? I picked a by all accounts crappy regional, but I held a line in two months and have an easily commutable, weekends off schedule in less than a year. If the industry tanked tomorrow and I got stuck here, I wouldn't make much, but at least I wouldn't spend two years commuting to a miserable 5-on, 2-off reserve schedule. (disclaimer, this isn't my main source of income)

Always pick somewhere you could get stuck at. Try not to commute if you can help it, but don't ever move for a regional.