For investing, many people here recommend Vanguard or Fidelity index funds, and there's a ton of great info in the Bogleheads site and books. You're looking for diversification and low expense ratios.
A big tenet of FIRE is to lower expenses now, and if you get used to that standard of living, they'll continue to be lower in retirement. If you need $80k/yr now, you'll need somewhere around that (minus work clothes/commute, plus more travel/hobbies) for retirement. If you cut the cable, drive a mustachian car, cook at home rather than eating out, etc., you might be able to live off of $30-40K now and the same in retirement, so the nest egg needed to support this is much smaller.
Once you have your nest egg, then use what matchewed said.