http://www.pokemon.com/ that's the official website..
www.serebii.net has a list of every Pokemon and shows where and how to find them.
Any website but in my opinion bulbapedia Also you can check out the pokedex.
go to Google and search Pokemon sapphire pokedex and it will give you a list of all the ones you can catch, you can also search for a national pokedex and look for treeko and that is the beginning of the sapphire/ruby/emerald pokedex(heres a link of the best one ive found sofar ... http://Lloyd.truepath.com/Jonathan/PKMNRS_Pokemon.htm ... ) go to Google and search Pokemon sapphire pokedex and it will give you a list of all the ones you can catch, you can also search for a national pokedex and look for treeko and that is the beginning of the sapphire/ruby/emerald pokedex
You must have Pokemon Emerald, Pokemon Ruby, Pokemon Sapphire, money, skill and knowledge. You also need friends help to trade and get the Pokedex full. After that, just ask to trade back. Also try your best to find all of the Pokemon in the version you have. Try and concentrate on finishing the Pokedex.
The best and easiest way to get Pokemon from Johto in Pokemon Ruby is to trade them over from other games (Gold and Silver). Pokemon from Johto can be obtained in the same generation Pokemon Emerald after the player completes the National Pokedex.
The best PokeDex on the Internet is at http://pokedream.com/pokerep/ it includes any possible fact you would need to know about any Pokemon. ---- If you are looking for a basic PokeDex though, simply go to the http://www.Pokemon.com website and search around the site for the PokeDex.
Compellati pokedex.
dialga is the best.
Ditto.
rayquaza
Pokemon snap or Pokemon emerald
you evolve a duskull at lvl 37 one of the best ghost Pokemon on emerald