1. Try to Hit Psyduck (in Blue Version) and Diglett (in Red Version) to move on to the next place. The more places you go or visit, the better chance you have of catching a rare Pokemon.
2. Hold the ball in the flipper for a few seconds before launching it. It will give you more accuracy for catching those "rare and valuable Pokémon."
3. Want to evolve some Pokemon into rare ones? If you light up all three evolution arrows, you can fire your ball into Slowbro's mouth (in the Blue Version) or into Ditto's Cave (in the Red Version), and you can choose which Pokemon you want to evolve.