To get onto the Cycling Road without a Bicycle, simply hold Left when you talk to the guard that warns you that you must have the Bicycle to enter Cycling Road. (If you already obtained the Bicycle, this still works if the Bicycle is in the PC.) In doing so, you will bypass the guard; if you continue onto Cycling Road, you'll still ride a bike.
Note: If you do this without a bike then you will only have one while on the road. When you leave the road, you will not keep the bike.
You need the HM Fly and Surf to do this glitch. Put the item you want to duplicate in the sixth slot of your inventory.
Go/fly to Viridian City. Talk to the old man that asks you if you are in a hurry at the beginning of the game. Answer no. Watch him show you how to catch a Pokemon.
Now you need to Fly to Cinnabar Island and Surf on the right side of the island (right against the edge). You should be able to battle a weird Pokemon called MissingNo. It's appearance is strange. Do not allow it attack you and do npt capture it as it will ruin your game! Just run away or beat him with powerful quick attacks.
After that, look at your sixth item in your inventory and there should be a strange symbol next to it. Do not worry, it only means that you have more than 99 of that item.
This trick is very simple. Find a patch of grass within the Safari Zone. Stand on it and just tap the directional pad lightly just enough that you turn without walking. You should encounter Pokemon and you have the option to catch that Pokemon or run and continue until you find the Pokemon you want without putting your steps up.
If your having trouble understanding this game get an english copy of a Pokemon game and write down what everything is, when you play green just refer to the list and (optional)write down the japanese names.