So im done my run of F3 and im going to start a save on New Vegas, i want to make a stealth character, but its my first time making a stealth guy and I want to know how viable it is.

Completely viable. Some would even say overpowered. Depends on your playstyle preferences and opinion, I guess. It starts out slow, because the key perk that makes it work really well, you don't get until level 12. That perk is Silent Running. If you like stealth play, be sure to get it. Before that, you can only effectively sneak up close on enemies when in 'walk' mode, because being in run mode while stealthing makes noise that will get you detected quicker. Unfortunately, walk mode stealthing is slower than petrified slug snot, and hardly worth bothering to do, unless you are a true masochist. But you'll get to level 12 fairly quickly, and once you get Silent Running, stealthing in NV rocks really, really hard. Be sure to put points in the Sneak skill regularly as you level up- I usually have it up to 80-90 by the time i hit level 12, so I can hit the sneaky ground running (so to speak) when I get that holy perk.

Also, wear light armor for best affect, heavier armors make more noise and will get you detected quicker. You can get by using medium armor if you're careful, and have maxed Sneak skill. Other tips- sneak up from behind your enemies, use cover as needed, use shadows to move in when you can, and sneak at night if possible, as darkness greatly reduces your enemies' detection distance. Oh, and you will end up with companions, and companions can really F up your stealthing a lot of the time. Sometimes you just have to tell them to stay put in a safe place, while you sneak into some situations. Their problem is they are way too reactive to the slightest hint that an enemy suspects you are nearby- even if the enemy hasn't spotted you or attacked yet, but is only in 'caution' mode, your companions will immediately attack at that point. Lousy programming choice, in my opinion, but we're stuck with it. With no companions along, you can usually stop moving or sneak into a cover spot, and the cautious enemy will give up and go back to picking its nose again, before long. That's the basics- enjoy!

Viable? Absolutely. You'll want Silent running plus the one where you move full speed while crouched.

Thanks to the sneak crit, plus my favorite class in general is a rogue, it's my favorite way to play.

With New Vegas, you will be able to add mods to your weapons. Silencers are very helpful for stealth so I suggest getting silencer mods for your weapons. I suggest getting the Professional perk if your going to use guns while sneaking. Melee weapons and unarmed also work well. The Ninja perk works well with this as it increases your critical chance and sneak attack critical damage when using melee or unarmed by 25%. Either way, sneaking makes for an excellent way to kill your enemies quick and quiet.

Melee and Unarmed, once you get enough Sneak and Silent Running, become whole different dimension of destruction.

I would also like to mention even if your companions are discovered and start to engage, you can still do sneak crits.

I wish companions wouldnt engage the enemy, even when set to Passive, until I went into [DANGER] instead of as soon as I entered [CAUTION]

That has been my dearest wish throughout my time playing NV. It really messes up the stealth game, with companions along. Unfortunately, I'm not really fond of soloing all over, either. And constantly going through the effort to make them stay somewhere while I go do (frequent) sneak attacks, then going back to get them, is just too much bother to mess with, except for rare special occasions when not getting detected is critical to me. I still cannot conceive of a really good reason why they chose to do it that way, unless it was to protect utter noobs and tactically-inept and unobservant fools. I suppose there are some of those types who would just get killed all the time wandering around derp-derp, if their companions weren't automatically set to defend them and alert them to unnoticed enemies as fast as possible. ED-E's silly ringtone every time he goes into combat kinda hints that may have indeed been the case. What an obvious (and incredibly annoying) dufus-alert that is. If that was the case, 'tis a pity the dolts got programming preferences over intelligent people, once again. Lowest common yadda-yadda. If that wasn't the case, then it was just a really, really stupid choice.

Hear hear. I remember last year there used to be someone who had in their sig something about how Action games were ruining RPG games and I cant help but agree. The gaming industry has fallen in step with the movie and music industry (here in the US anyway) in that they make crap that will sell to the largest number of customers for the least amount of input regardless of how poor the quality or level of creative thought. Pop music, FPSs or licensed games, popcorn summer action flicks or RomComs etc etc its all crap

case in point our friends at Obsidian had to start a Kickstarter program to fundraise for their own inhouse RPG -- the kind of game they got into the industry to make only to find that the industry wont allow them to make those games and be commercially viable

You do have to aware the companions doesn't possess the Ninja master level of stealthiness; especially lacking in Silent Running.

How about the invisible Lily stepping in front of you every time you go for that stealth kill? I have shot two unique weapons out of her hands, never to be seen again.

Yea I hate that, especially as I play in third person, when my companions bump me from behind it throws off the camera. Ive learned that the best thing to do is not to move left or right or ahead (as this will cause the companion to move closer again) but to take a step backward