So as the title says, I want to make an Assassin Character/Thief. I need help though, I'm not sure what to train other than one-handed (for Single dagger Damage), Sneak, & Pickpocket.

My question is:
What other skills should I raise? And what are some tips for playing, and leveling my Assassin/Thief Character?

Alchemy and light armor and you are set.

My Assassin/Thief is mainly

• Sneak (went towards Dagger dmg multiplier first)
  
• Archery
  
• One Handed (I wield a sword when sneak is blown and no longer get dagger multiplier)
  
• Lockpicking (trains itself, only a couple of perks spent though)
  
• Light Armor
  
• Smithing (I went the Heavy Armor side to get Daedric for the weapons, I'm happy with the quest armors)
  
• Enchanting

I never focused much with Alchemy since as a Thief I find more than enough potions/poisons to fill my needs.

Sneak (nearly maxed out, although maxing fist perk isn't needed), Archery, One-Handed (dual wield route, up to power attack bonus, make sure you use dual wield power attack with daggers for backstabs). If you want to be really overpowered, take Smithing (heavy armor route so you get Daedric weapons) and Enchanting (dual enchant isn't needed, but it's nice). I found Light Armor to be useless for a (good) thief. I'm lvl 45 now on Master difficulty and my Light Armor skill is at 50, that's how little I get hit. This is for perk selection of course, obviously you'll train other skills as you play, such as Speech, Lockpicking and Pickpocketting, but putting perks into them is kind of a waste.

Your playstyle will be sneaking A LOT and getting those sweet x3 bow and x15 dagger multiplied openers on enemies .

edit: Seems that Denver beat me to it.

Just to add what he said, obtain the Dark Brotherhood gloves for double the backstab damage, so 30x, deadly.

The biggest, most important of all is sneak. At high levels you are near-invisible. It's the most important tree of your build, no doubt, and you'll pretty much want everything in it, although I find that 2/5 for the first perk is enough for me, and I'm at skill rank 94 at level 38.

Light armor and daggers are indeed key. Also, your best light armor is dragonscale, so smithing is also recommended in my book. You can also improve the armor with it for even more protection, and you will pick up glass smithing on the way to make some neat weapons. In the endgame, you will reach the cap on armor (80%). heavy armor gets there faster, but is heavier.

I personally disagree on alchemy being a must. My backstabber doesn't use it. The potions I randomly find are sufficient. It's very viable though, and a good way to go if you like.

Next is up to personal taste. I use the following:
Archery: you need some sort of ranged attack, trust me, and archery has a x3 sneak attack perk you need to pick up on the x15 dagger sneak attack route, so it's perfect. Also, you can fire an arrow at a location to distract enemies. They will investigate where the arrow landed. Lasltly you can trigger traps with it. In my opinion it's a must.
Smithing: Making, and then improving, your own weapons and armor is perfect and powerful in the game. It's very easy to level by making iron daggers and leather bracers. You can take it straight to 100 if you are so inclined, although that may unbalance the game somewhat. In your favor, that is. Still, not that fun. I personally set a rule I will never buy crafting materials from merchants, and only will use what I find in the wild. It also gives an incentive to hunt deer and explore mines. It also ensures you keep in line with how powerful the game expects you to be.
Restoration: A quick heal in a tight spot is divine. Also has 100% spell blocking shield spells, which help you if spellcasters have spotted you. As an added bonus there are perks that speed magica regeneration and save you from death. All in all it's a good package.

Others I don't use:
Illusion: It has muffling spells which make sneaking easier and at higher levels invisibility. Very powerful when your sneak is low. It also has perks that make spellcasting silent. Ideal for daggermagi. I used the muffle spell quite a bit at lower levels so I could sneak up to enemies which would normally notice me, but never invested perks in it.
Lockpicking: You will be doing it a lot. And I mean a huge lot, no matter what class you play. It doesn't add all that much though, but it removes a frustration. *damn you master level locks...* Still, by the time you encounter master level locks you will have enough money to buy a thousand lockpicks anyhow. there are a few interesting perks that promise more loot, so it may be rewarding. There is, however, one birthsign standing stone that allows you to bypass most locks. Still, there's better signs out there, which makes lockpicking the only way to open locked chests.
Pickpocket: Sometimes nice to get a key in my opinion. I find that a silent dagger to the back is a quicker road to Rome though if you want something from a person. Still, it can be fun I suppose. The 100 carrying capacity perk certainly appeals to everyone. But I'm not impressed.
Enchanting: It's good, I'll be honest. I prefer smithing though. Combining the two will make one too powerful in my personal opinion.
Speech: So now you got the loot, but you need to sell it. Speech is mostly about bartering, and will help you get more money for your goods, allow you to fence goods to more people, etc. For the thief in you there's the 'bribe guard' perk.

Things to avoid:
Magic: Unless you want to be a daggermage, I'd stay away from destruction, alteration and conjuration.
Block: You want a quick and silent kill, not a prolonged battle. Go dual wield.

One handed
Sneak
Light amour
Alchemy

tho are what you should be working on till you end around lv50 anything after that just dump in pickpocket / lockpicking / speech etc since the game will scale to your level till 50 working on combat skills frist will always make you life easier anything else can wait till after lv 50

It's really based on your perfered playing style but for an idea this is what I went with and I'm loving every second:

Raven Shadowsong - Imperial Spellblade

One-hand (swords and daggers)
Archery
Sneak
Light Armor
Destruction (fire and frost spells)
Pickpocket (for the poisoned perk)
Smithing (only 1 point for Arcane Blacksmith to upgrade enchanted weapons)

Note: The only reason I didn't go full out Enchanting, Smithing or Alchemy is because I feel it makes the game to easy but that's for you to decide

Enjoy :tongue:

Sneak, one-handed, archery(especially the zoom and time slowing perks), alchemy, light armor. Don't waste your money on sneak training, you'll max it out long before any other skill as long as you always sneak in dungeons. Some people might disagree with me on this, but I've found that some illusion spells, especially fury, are lifesavers in situations where you have to fight multiple enemies. Lockpicking is pointless as long as you have plenty of patience and lockpicks. I've only spent one point on pickpocketing, but I imagine that it would be helpful when you're doing the Thief's Guild and Dark Brootherhood quest lines, but I don't know if that makes it worth spending points on. I have a level 30 assassin, and my only regret is that I haven't spent a single point on enchanting, magical bows and daggers are quite rare.

As for general gameplay: find a good sniping spot and wait until night when you come across enemy encampments. If you encounter multiple enemies in a room, shoot one of them, retreat into a dark corner of the room you came from and backstab them when they come looking for you. Play with headphones and pay attention to sounds, you'll hear most enemies before you see them. And never ever ride a horse or you'll be saber cat dinner in no time.