Early Game:
* Charmander: Found in the Viridian Forest (before you enter the gym).
* Vulpix: Found in the Viridian Forest (before you enter the gym).
* Growlithe: Found in the Rock Tunnel (after you obtain the Flash HM).
Mid Game:
* Ponyta: Found in the Route 16 (south of the Celadon City gym).
* Magmar: Found in the Victory Road (before the Elite Four).
Late Game (after the Elite Four):
* Flareon: Can be evolved from Eevee (found in the Celadon Game Corner) with a Fire Stone (found in the Seafoam Islands).
Other Fire-Type Pokémon:
* Houndour: Found in the Safari Zone (available post-game).
* Houndoom: Evolves from Houndour by leveling up.
* Slugma: Found in the Mt. Mortar (available post-game).
* Magcargo: Evolves from Slugma by leveling up.
* Entei: Can be obtained from the "Fire Red" event in the game (rare).
Tips:
* Trainers: Watch out for trainers in the various locations, as some will have Fire-type Pokemon.
* Use your Pokemon Trainer Club: You can find detailed locations of all Pokemon on the Pokemon Trainer Club website.
* Use a guide: There are numerous guides available online that can help you track down all Fire-type Pokemon in FireRed.
Remember that these are just general locations. The exact encounter rates of these Pokemon may vary, and some may require you to have certain badges or items to find them. Happy hunting!