You will need to specify which of the Bases you need help with.
1) Mt Moon - Literally follow the path round
2) Celadon - Neogiate the directional tiles.
3) Lavender - With Silph Scope head to the top and defeat them
4) Saffron/Silph Co. - You need to obtain the Card Key on Level 5 (you will need to go through and then back through the warp tile), then open the door on Level 3, and step on Warp Tile. Straight forward from there, don't miss all the items there.
5) Island One - Requires you to beat the elite 4 and get given the task by Celio. You will see where the base is by the Rockets standing there on your first visit.
6) Island Five - This requires the Ruby to have been obtained first, and head to Island Eight, to obtain the second password (the first will come from going to the first Island base and I won't spoil why you then need to go to the base) and head through, luckily one of the Rockets will change the direction of the Directional Tiles when you defeat her allowing you to go for a heal.
Go up to Lake Rage and catch the shiny Garydos. Then go through the Rockets Hideout.
you have to get the key after beating a team rocket guy then its on like the 4th floor where u have to get through a bunch of spinny thingsnowherei believe it is 'green leaf'
you cannot catch celebi in Pokemon leafgreen. you can only get it through cheat codes or trading.
Watch leurois Pokemon leafgreen walk through part.
IMPOSSIBRUUU!
Easy first go up to mt ember on one island then go to where there are two rockets battle them and then go through the hole find your way you find it
chach a rear leaf Pokemon that fly
Your have to hit the Pokemon statue switches
Through Min Settings in mystery Gift
You cant get him. I think its only through an event.
You can only get Deoxys through a special event.
zapdos, at the power plant down from the rock tunnel you have to surf there