Advanced forms
There are advanced forms of some pokemon like Lightning Picachu and Surfing Picachu and Singing Jiggly Puff. These will get you higher scores than just a plain one.
Dragonite
In the valley stage, when you get to the whirlpool, throw some pester balls into it and Dragonite will appear.
Get Charizard
When you get at the end of the volcano level you will see Charmeleon running around a lava pit. Knock him in it with a apple or pester ball and he will come back out as Charizard.
Get Muk
In the Cave there are two grimers. Take lots of pictures of them. When the third appears near the three bulbasaurs, take a picture. Now throw lots of pester balls at him. He will evolve into Muk.
Ghost Photos
In the first tunnel, take pictures of the purple myst that floats around. When they develop, It will be one of the ghost trio (Gastly, Haunter, Gengar).
Helpful Hint
It is easy to get a picture of a pokemon, but if you want a high score then you should try to get a picture with more then one pokemon and one if them in the center.
Magenite
In the volcano level throw apples and they should come together and before they come together you should be able to get a good shot of one of the three.
Mythical Birds
Each of the three birds will be in an egg.
The first Mythical bird is Moltres (he is in the Volcano level), he will be easy to find since his egg is blocking your path. all you have to do is hit the egg with pokemon food or pester balls and a moltres will emerge from the hot lava
To get Zapdos you must lure pikachu to the egg sitting in the tunnel then play a pokeflute. If you did it right pikachu will hit the egg and he will shoot the egg out and the egg will blow up revealing Zapdos.
Articuno: Play your Pokeflute when you see the Jynx and the egg.
Speed Pikachu
Right before you leave The River, you will see a Pikachu sitting on a fallen tree branch. If you hit it with either a Pester Ball or an Apple it will fall backwards. Get your camera ready because it will zoom around that area so get a close picture right after you hit it.