It all depends on the pokemon. Some need stones,some need to be leveled up, and some need to be traded to evolve. These are haunter , machoke, graveler, and kadabra.
In Pokémon Yellow, Charizard is not capable of evolving.
it depends on the Pokemon that are evolving
Well, it depends on what Pokemon it is.
If you stop a Pokemon from evolving, it`ll try to evolve every level after that unless it`s holding an everstone.
Spearow evolves at level 20 in Pokemon Yellow.
It doesn't evolve by itself you have to give it an evolving stone
It should evolve at Level 55.
If you accidentally pressed "B" while your Pokemon was evolving, all you have to do is level it up again.
when your Pokemon is evolving press b and a when your Pokemon is evolving press b and a
It depends on which Pokemon it is because they all have different evolving levels.
You just need to level it up a bit and it will evolve.
At level 31 it will evolve Enjoy =]