Fallout 3

This thread is all you need for this achievement:

http://www.xbox360achievements.org/forum/showthread.php?t=10...

A list of a LOT of terminals (more than enough for the achievement) and their difficulty.
Credit goes to RaidenX49 for the entire guide, but I don't think anyone on this site should have to sit through this achievement without this guide by their side :D

If you science skill isn't high enough to get the majority of these, remember to use the following:

Lab Coat (Obtaining from Vault 106 is the easiest method)
Mentats
Science bobblehead (See Vault Tech CEO)
Any +science or +INT items.

NOTE: Rather than saving, you can try 3 words, then just press B if you don't have it, and you can cancel out and go back in for 4 more goes, note that the code doesn't stay the same, but this method makes it impossible for you to fail.

These are all the locations for the Terminal's on Fallout 3

http://fallout.wikia.com/wiki/Terminal

Many thanks for Fallout Wikia for the info.

Before you give me a negative vote, please explain yourself why you did it and I will be more than happy to improve my solution. Thank You.

If you want to go for this achievement, I suggest getting your science skill up to 75 first so you can hack 'hard' terminals, you are not required to reach 100 science because there aren't many very hard terminals. Off the top of my head here were the places i visted with many terminals and the approx number of terminals that were there.
-Rivet City Has approx. 6-9 terminals, look it all the rooms, and travel up the stairwell to reach the guard HQ and there are a few there.
-Vault 87 has 7 terminals, 6 which are 'hard' and one average. they are around the area that you find fawkes in the main quest.
-Museum of technology has 3 terminals
-Arlington library has 3 terminals
-2-3 terminals in the underworld
-3 terminals in tenpenny tower
-4 In megaton, there is 1 in the saloon, in the back room, 1 in children of the atom's church, 1 in the bar near the center of town and another in the craterside supply.

Terminals are in most places you'd think they'd be. Metro areas, any place with turrets, some character rooms, stores (like in Tenpenny Towers, etc.)
The frustrating thing is searching for them.
The key to success is to save before attempting a hack. If you fail you simply reload and try again.
In the event you come across a terminal with a high skill level take MENTATS to raise your skill to be able to attempt the hack.

And always, always SAVE before you attempt!

Some advice to help hack harder terminals: if you see matching quotations or brackets with any assortment of random characters between them, i.e. (#@!AV), {[]}, [||], etc, - you can highlight that entire thread, and clicking it will give you one of two bonuses: either replenishing the number of attempts you have, or even better, removing one of the wrong words entirely. In some cases you may even be able to remove every word except the correct one!

Another tactic, albeit cheap, is to simply guess the first word that appears, and if it isn't right, immediately back out and try again. It can perhaps be faster than trying to work it out even on Very Hard terminals, given how fast you can retry to hack.

Since there's already a location on all terminals, here's something to save you MUCH more time:

http://mediumexposure.com/dev/f3hack/

Enter all the words ONLY, separating them with spaces, enter 4 at the bottom, and hit enter. Just guess the words it gives you and unless you made a spelling mistake/typo, or you're giving the program the wrong amount of letters you got right, you'll get it every time, regardless of difficulty of the terminals.

this is a very helpful video guide of more than 50 terminals in the main game of fallout.
follow this guide to get this achievment simply. now have fun

This solution is pretty simple. There are way more than 50 terminals in the Wasteland, ESPECIALLY if you have DLC's loaded, particularly, Point Lookout, Broken Steel, and maybe The Pitt but I doubt it. Hacking terminals is easy - but it depends on several factors.

Your personal skill at hacking terminals - ability to find duds and compare words to find the correct password
In game science skill
Terminal Hacking Difficulty

I find that the Very Hard terminals are as they say, Hard, while the Hard and Average terminals are actually the easiest with a high science skill. The way it gets easier is this: if you have a high science skill, there will be more duds in terminals when hacking. I recommend waiting until you have at least 75 science skill before starting, and keeping track of where all the terminals are, or else it could take a while for each terminal. Also, you should use a terminal location guide - very helpful.

When you start the game, only put 9 points into Intelligence - because the Intelligence bobblehead is accessible from the start of the game. When you leave Vault 101, look on the map for the Potomac River, and follow it south. When you've reached the Jefferson Memorial, look East and there's Rivet City. The Intelligence bobblehead is inside the Science Bay of Rivet City. Now you have 10 Intelligence, and Intelligence affects how many skill points you get every level to spend on skills. Now I recommend putting 5 points in science every level, and taking the Educated, Comprehension, Swift Learner, and Daddy's Girl/Boy in that order, to maximize how quickly you level up and how many points you get, etc. Don't read ANY skill books like Tumbler's Today for example until you get Comprehension, because then you get 2 skill points instead of 1.

Also, if you follow this, you can put 5 points every level into your speech and barter skills, making the Silver Tongue Devil Achievement much easier to achieve.

Finally, if you want the best start in Fallout 3, follow my steam guide here: http://steamcommunity.com/sharedfiles/filedetails/?id=572292...
There are plenty of ways to get an amazing start to Fallout 3, for either karma (but Good Karma gets a better start).