Step by step: br Heal your team at the Cerulean City Pokemon Center br Head up Nugget Bridge br Go left until you're right in front of the first patch of grass br Take one step south and immediately press start br Use Abra (or any other Pokemon that knows Teleport) to Teleport back to the Pokemon Center br Battle the first trainer in the Cerulean Gym br Defeat his Horsea br Use Growl on his Shellder at least 6 times (Each Growl reduces Mew's level) br Go back up Nugget Bridge until the menu opens itself br Close the menu and Mew will appear at LV1 br Use a sleeping attack to put Mew to sleep br Throw Pokeballs at Mew only if he's asleep (He will dodge almost every ball if he's awake. This will take a few tries.