Here are the common ways people obtain rare Pokemon like Mew:
* Events: Some games have special events where you can receive rare Pokemon, but FireRed doesn't have any official events that would give you Mew.
* Cheats: Using cheat codes or save editors can allow you to obtain Mew, but these are considered cheating and can make the game less enjoyable.
* Trading: If you know someone who has a Mew on another version of the game, you could potentially trade for it.
It's important to remember that if you want to experience the game as it was intended, the best way to play is without using cheats.