As you head up to Route 24, you will have your second battle with your Rival. After defeating his four Pokémon, you will have to fight 6 trainers guarding the bridge. You may have to visit the Pokémon Center several times, but in the end you'll be rewarded with a Nugget which you can sell to get some cash. At the top of Route 24 you'll find TM45 and Damien Who is having some Problems.
Charmander
Charmander is easy to get, just get passed the Nugget Bridge to the north of Cerulean City.
Up and to the left is Damian standing next to a Pokeball.
Respond "Yes" to his question to get Charmander.
Then go right to get to Route 25
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