Early Game:
* Route 32: This is probably the easiest place to find an Eevee. It appears relatively frequently in the tall grass.
* Route 34: Another good spot, with slightly higher encounter rates than Route 32.
Later Game:
* National Park: After you've completed the main game and entered the National Dex, Eevee will be available in the tall grass here.
Tips for catching Eevee:
* Use a Pokemon with False Swipe: This move will reduce your opponent's HP to 1 without risking a knockout, making it easier to catch.
* Use Poke Balls with higher catch rates: Ultra Balls and Great Balls have a much better chance of catching Eevee than standard Poke Balls.
* Consider using a Dusk Ball: If you encounter Eevee at night, a Dusk Ball will dramatically increase your catch rate.
* Try to lower Eevee's HP: The lower the HP, the easier it is to catch.
Remember: Eevee is a relatively common Pokemon, so don't be discouraged if you don't find one right away. Just keep exploring and you'll eventually come across one.