Any assasin/thiefs out there that have some tips for a ES rookie?
Yo! All of my TES characters usually start as a thief assassin and then my 2nd one is usually a battlemage. This time around I chose bosmer instead of dunmer. Anyway on to tips! ARCHERY is the first rule to being stealthy. Use archery always as your first weapon it has seriously been so greatly improved in this game that you can usually end fights before they get close enough to damage you. Other weapons you should have are daggers. You can dual wield them if you want, but personally I think that using 2 weapons at once is crap and usually willl just get you killed, because the whole point of being a thief is to try to stay AWAY from your enemy. Not close like the dual weapons require you. Staying on the topic of keeping enemies away though do NOT invest in block. It's a waste of time for a thief. It's seriously an awesome thing to have on other characters, but as a thief it will kill you. Lastly Invest a fair amount of time into conjuartion(spelling?) specifically necromancy, destruction, and illusion. I would also say throw some restoration in there just because that is useful no matter what character you play as. Also poisons/debuff potions don't hurt either

On to armor! Use ONLY clothes or light armor. When in a non-combat area I would suggest tossing off that armor and slappin on some clothes. The reason for this is simply when sneaking (which I might add is a wonder in this game, and a MUST have for thieves/assassins. Certain perks for sure, but we'll get to that later!) clothes will produce NO SOUND. Which greatly helps getting around if you're stealing from people or stalking someone. Light armor is the armor type to go for as well, because it allows you to move swiftly, and also again less sound than heavy. Another reason that these two dress styles are useful which I've noticed a surprising number of people don't know is that armor effect magic. The less armor you have the better your magic will work(and magic is the last line of defense for these types of characters).
On to fighting styles/some useful perks! Since you have been a warrior type I'm sure you are used to running in and destroying all who oppose you with heavy swings and bombs lol. As a thief/assassin you will destroy all enemies, but in a much sinister way...which if you ask me is very rewarding. Okay the thing you want to stick to as this character is stealth of course! Sneak always and when you can. If you want you can try to sneak past everyone which some people like and needs no explaining. I play a little differently..and like to punish all who would do me harm :] so like I said earlier what is a must as a thief/assassin? ARCHERY! There are some perks in the sneak section that add buffs to the amount a sneak attack arrow will do which are useful, but you can probably get by without them. Most arrows (after a good bow and investing money in top of the line arrows) will one shot enemies with a sneak attack. If you fail to get the killing shot though and then enemy starts looking for you have no fear! keep your cool and use the new system of sneak/archery in this game to mess with your target. In skyrim if you shoot an arrow at a distant corner while sneaking and not seen the enemies will go to investigate that area. Just try to get the enemy away from you as quick as you can! If thise fails though prepare for combat as a thief.... as a thief/assassin close combat can be stressful...and frustrating...I play on the expert/master difficulties so it's goes without saying I die sometimes. If you play anything lower the game seems too easy but play how you play. Anyway what you wanna do is get your sword/dagger (prefered dagger for the speed) in your right hand and spells in the left. Try to kill the enemy right away with the spells, but if it isn't working will and you need to use the dagger try to coat it in poison, or a potion that makes the enemy weak against magic. The purpose of the potion to weaken the enemy from magic is you REALLY, REALLY, REALLLLLLY want distance in the fight. Don't try to block just dodge and look for an opening.
Hmm this got a little diorganized...oh well I'll just keep going! haha it's just so much to explain! It took me forever to work out being a thief, and then skyrim just comes in and adds 100's of extra tactics. Fighting as a thief is just all tactical...like the necromancy I mentioned earlier...say you stealth shot a guy killed him, but the 2nd guy saw you...you would use the necro to summon the dead to attack him..slap a calm on the enemy so you have time to leave...use the calm to summon the dead, and just ahh soooo many possibilites.. let me just say a perk you MUST have is the sneak one that lets you be 20% harder to see when sneaking. Invest in that as much as you can. I even completely left out pick pocketing and lock picking...really just kind of play around with everything...if you have questions just ask me lol. My gamertag is WorldsBestRabbi and my Steam ID is the exact same thing. I play skyrim on Steam, but I'm usually always on xbox to chat. If you have PS3 well...you have my skyrim forum account name lol. just message me I'm on often!
I HOPE YOU CHOOSE TO FOLLOW THE STEALTHY PATH!