One of the strangest Fire Pokémon, but quite good in the UU environment if used correctly. That Attack is outstanding, and will certainly do a lot of damage if you time its use correctly. Hey, it's better than Magcargo at least.
Flareon, the forgotten one of the Eevee evolutions, is a highly useful underused Pokémon that can catch your opponent off guard. That monster attack is going to hurt a lot. Your primary attack will be Return, use Shadow Ball on anything that Return cannot hit. Flareon's Special Attack is pretty high as well, and with STAB, Overheat can be effective against the folk with higher Defense, like Steelix and friends.
The last attack is up to you. Hidden Power Grass is there to take out the Rock/Ground-types, and do some good damage to Swampert (although you really should only use Flareon in the UU environment anyway.) No, it's not enough for an OHKO, but you at least have a chance of knocking out an unhealthy Golem. Hidden Power Fighting and Shadow Ball together are unresisted, and at least Hidden Power Fighting runs off Flareon's large Attack. Quick Attack is also useful, as it runs off that huge attack power, cancels out Flareon's low Speed, and really can save your Flareon in times when you need it the most. Both good moves, just go according to preference.
Erm, OK. Well, Curse can be used with Quick Attack if you're into that, and if you pass some Speed to it, it can do some damage with Subflail (I don't recommend this at all by the way, but it's always there for consideration.) Charm is a good move that can force a switch, and negate the destructive effect of Earthquake somewhat. Wish is just there as a suicide move, giving another one of your Pokémon something nice before it dies. And Body Slam is there as a possible replacement for Return, as paralysis is always good, especially on this slow little Pokémon.
OK, well it's not going to outrun a lot of Pokémon, so max out that Attack, with Brave. You should stick some EVs into Special Attack to give Overheat something to run off (and a little bit more if you want to go with HP Grass.) The rest is up to you, I usually just chuck it into its HP or Special Defense.
Checks and Counters
That high Special Defense will not protect it that well from powerful Water attacks, due to its low HP effectively canceling it out. Its main weakness is the Rock/Ground-types that run rampant—Hidden Power Grass isn't enough for an OHKO. Fast Normal sweepers with Earthquake are probably Flareon's greatest threat, so beware Kangaskhan and friends.