tleilaxu said:
Trust me, you only need three levels of Rogue
1: Rogue (max skill ranks 4)
2: Wizard (5)
3: Rogue (6)
4: Rogue (7, giving you 7 ranks in decipher script, escape artist, and the other one you need)
Check again.
PHB p. 59 clearly shows the Decipher Script is a Rogue and Bard exclusive skill.
PHB p. 56 clearly states "If a skill is unavilable to a class (that is, if it's an exclusive skill that a multiclass character's other class doesn't have access to), then levels in that class don't increase the multiclass character's maximum ranks."
They give an example of Use Magic Device, but if you check the skill table you will find that Decipher Script is also an exclusive skill.
You need for levels in a class that has Decipher Script as a class skill. Although this is provided by a few different PrCs (such as LoreMaster), the easiest way to get it is to take 4 levels of rogue and/or bard.
The build that tleilaxu gave doesn't work.
Never trust someone that says "Trust me."
By the way, the requirements for Arcane Trickster are:
Any non-lawful alignment
Decipher Script, Disable Device, and Escape Artist: 7 ranks
Knowledge (Arcana): 4 ranks
Spells: Ability to cast Mage Hand and at least one arcane spell of 3rd level or higher.
Special: Sneak Attack 2d6
The easist way to do it with Wizard is Rogue 4 / Wizard 5.
Edit: Forgot closing quotes.