Tricks and codes highlighted in Blue are confirmed by me - ones highlighted in Purple haven't.

--HOW TO CATCH POKÉMon in the SAFARI ZONE - THE EASY WAY!

First of all, go to the Safari Zone. Hang around in an area where there is a Pokémon that you want. Say you want to catch a Tauros, but they're too hard to catch. Walk around the grassy area where Tauros is. Wait for time to run out, then make a Pokémon use the FLY HM Technique and fly to Cinnabar Island. Use a Pokémon that has the SURF ability, and surf on the shore that is to the right of the Cinnabar Island Gym. Make sure to only surf ALONG the shore -- not next to it (it looks like you're surfing on a sandbar). Eventually, you'll encounter some of these Pokémon, only this time, you can catch them with Great Balls.

--POKEBALL SECRET: **I, myself, couldn't get this to work, but the other players who I asked said it worked for them**
Throw any kind of Pokeball (Greatball, Ultraball, or Pokeball),
and after it is released from your hand, hold UP + B.
The ball will act like a Masterball! It works, but takes a bit of
practice to get right. The trick works on both versions.

--TO GET MEW (Not Mewtwo):
You'll need a Gameshark for this, and then after you put in the code and start playing, go to any grassy area and fight!

0115D8CF

--How to get infinite items

Make a Pokémon FLY to Viridian City. Remember that old guy who fainted in the beginning of the game, then was well after he got his coffee? Well, talk to him again, and when he says, "Are you in a hurry?" answer NO, and he'll show you a demonstration of him catching a Weedle.

After this is done, make a Pokémon FLY to Cinnabar Island. Place whichever item that you want to be infinite (good examples are Rare Candy, Master Ball, and those ability enchancers sold in Celadon City =D) in the SIXTH (6th) slot from the top in your item inventory. Make another Pokémon SURF along the coast next to the Cinnabar Island Gym. You'll eventually meet up with a Pokémon with a garbled name. Whatever you do, DO NOT CATCH IT, nor fight it! Run immediately, as this is a glitch Pokémon, and you run the risk of losing all your Pokémon! If you run without a fight, you'll be alright. His name might also be MISSINGNO., but they're the same Pokémon. Don't catch that one either. It'll delete your Pokémon.

When you run, and look back at your item screen, the item may have a graphic, may it be a glitch or a flower, for example, but don't worry - that's perfectly fine! You can use an item 120 times. When the item goes from glitch-# to the single digits, possibly even 0, it isn't. It's just in the 100's. Check for yourself - click on the item and select Toss, and you'll see you'll have more than 0. You may repeat this process as much as you want!