Fallout 2 Tips
Being a gamer myself I know that every once and a while one just gets stuck. In order to relieve the agony of not being able to get past that one little part or do that frustrating task, here are some tips to help people out. I do not like walkthroughs personally since it is essentially someone else's game you are playing. Hopefully this will be very informative and helpful while still allowing people to play the game their own way.
Entering the Sierra Army Depot
First battle through the Turrets surrounding the entrance. In the small shed to the left is a bunch of boxes. A howetizer shell lies in one of them. Pick up the shell and carry it to the large gun in the larger shed to the right. Use the shell on the gun and it will blow up the front doors of the base.
Installing the Hydroelectric - Magnetosphere Regulator (Gecko)
1. Talk to the tech goul in the extreme right of the reactor and tell him to install it.
OR
2. Operate the computer behind the red-code doors. Drop the hy-mag into the slot it tells you. To hack into the Enclave
network type the codes in this order (9X7299, 70Y644, 008721). You will find that there are no operating directions on the
Enclave server. You will have to type in a program manually. Use the following order: 
this will have the robot install it for you.
Entering Vault City
Two things will get one into the rest of the city, one is a Day Pass, the other a full citizenship status. Being a citizen grants additional priviledges such as staying in the city after dark, entering the Vault, and the lack of personal searches upon entrance to the city, enabling one to smuggle illicit substances. (Illegal things are needed for some quests, however one's party members are not searched and goods can be smuggled in their inventories). See "Becoming a Vault City Citizen". A day pass can be obtained from the customs office in front of the gate. Simply tell the officer that you have buisiness with the First Citizen. A fake citizenship can be bought from the other customs worker in the front room. It is a forgery and thus will be dangerous to be caught with. The gate guards cannot tell the difference so it grants entrance to the city. However with the forgery, the night guards, and Vault guards will question your status, as will the First Citizen. She will not remember making you a citizen. This is not always a problem if one is Good Natured and/or has a high speech skill.
Becoming a Vault City Citizen
Two ways exist that I know of to become a citizen. The first is to talk to the Vault City representative, fix the plant in Gecko, and then tell him. He will then give a full citizenship in thanks. The other way is to talk to the Corrections officer. Tell him that you will destroy the raiders. Then go kill them. When he hears that they are wiped out, he will have you talk to the First Citizen. She will give you money and a citizenship.
How to kill Roger Westin (NCR)
This mission is given by Mr. Bishop in New Reno. The murder must not look like a hit which presents the only real difficulty. First go to the doctor in the middle of NCR. On the selves behind him are a hypo of Poison and a bottle of Pills. The doc doesn't want people messing with these dangerous items so it will take 20+ Sneak still to take the pills and 30+ Sneak to take the Poison. After these items are obtained you must find a way into Westin's Ranch. To get to Roger Westin you have to pass through the security gate on the west side of NCR (when you enter for the first time go South once, into the actual town, then West once to Westin Ranch). The guard will not let you pass unless you have business with Mr. Westin. Talk to the sheriff on the corner or the trader in the building below the gate and ask about local jobs. They will tell you about Westin's employment needs. Tell the gate guard you wish to be hired and he'll let you in. I would complete at least the first job for Westin before killing him since it is easy and gets experience (the second job, the caravan job, is very difficult). But anytime you access his ranch you can kill him. To finally kill Westin properly, poison him with the hypo and put the pills on his dead body. Everyone knows he has heart problems and will assume he died of a heart attack.
How to 'wack Earlson' (NCR)
Earlson is located in the secure compound at the South-Westernmost part of NCR. The Presidental Pass (NCR) is required to get past the gate. The pass in found on Tandi's Aide. Steal it from him and show it to the guard. Earlson may be killed straight out but this will likely cause a gunfight involving you versus the town of NCR. To kill him and avoid any messy conflict use a BB Rifle and aim through his southern window. One or two aimed shots should kill him allowing you to run away. None of the guards should realize that he is dead. This will allow you to visit the town unharmed in the future.
How to enter the Military Base
First you will need an explosive, either Plastique or TNT. At the base there is a mining cart in front of the rubble. Find the Pole lying just below this cart, it will be highlighted by the cursor. Pick up the pole and use it on the cart. Then click on the pole and select the "use item from pack" command. Click on the explosive and set the time for at least 20 s. The explosive should now appear on the pole. Push the cart using the hand command. The scene should cut away and be replaced by one with the rubble gone and the cart overturned. You can now enter the base.
Getting Fuel in the Tanker (San Fran)
Several methods exist. San Fran has a couple people who can hack into the Shi network and transfer fuel. Badger in the Tanker can do it, but first you must save his girlfriend from the aliens / floaters down below. After saving his girlfriend he will do you a favor. Ask him to transfer fuel... The civilian above the Hubologist base can also help you. First talk to him and find out that he is in love with the female female Hubologist star. Next go down the stairs, into the Hubs base, and tell her that the civilian likes her. She will say she thinks he is cute. When you go back up and tell him this he is grateful enough to transfer fuel for you. There is also a Shi scientist in the temple who is interested in polymers. If asked how to get some fuel, he will require hardened power armor. Power armor can be found in the Brotherhood's base in San Fran. To harden it, talk to the hubologist scientist in the depths of the hub's base. He will agree to do it for $10,000. If your speech is high, you can convince him to do it for free. He will only harden two sets of armor so you are somewhat limited unless you've already found the advanced power armor.
Surviving the Puzzle Room (Enclave)
This room is the nastiest part of F2. Here is the overview:
There are nine sections with electrified floors, you enter from room B. Room G
has a little wire hanging from the wall
that I assume can be cut somehow to shut off the electricity, but I don't know how to cut it. Operate the computers in the
rooms in this order as displayed above: B-C-B-A-A-H-G. This will open enough doors so that you can exit in every direction
including the bottom to complete the puzzle.
Killing the President (Enclave)
There is a way to kill the president without getting into a fight with the guards. Use 6-8 super stimpacks on him rapidly then rest. The stimpacks will cause damage as they wear off and that many in a row is enough to kill him. You can then take the pass key and no other NPCs are wary. [I admit I am curious if using the posion on him would do the same].Beating the End Boss (Enclave)
The last boss is a mutant in Advanced Power Armor. He is twice as tall as a human and many times stronger. To kill him with little difficulty you will have to prepare. First kill the President of the United States and take his passkey. You will want that later. After blowing up the Enclave main computer, run up the fire stairs and talk to the patrol of armored guards. Convince them to fight with you. Sneak into the main room (the one you first entered the base through), and stay to the bottom of the screen. Sneak to the computer and use the Presidental Access Key to initiate "Counter Insurgency". The turrets will now shoot the strongest in the room, which will be the boss. When you attempt to leave he will appear, and the turrets, armored guards, and yourself can all kill him. He shouldn't last more than three or four turns. Aim a guass rifle to his eyes for added damage.