Multiclass

[Vardandor]

Ok i have a level 10 bard and want to multi class him with a rogue how does base attack, saves, etc stack. Also if i level to 11 would that level mean my rogue level would be at 3 or 2 because 1 level from 10-11 would be worth a few low level levels in terms of xp.

[TOZ]

Add the BAB and saves from your new class to the BAB and saves from your old class.

A 10th level Bard has BAB 7, Fort 3, Ref 7, Will 7.
One level of Rogue adds 2 to Reflex.
Thus, your characters has BAB 7, Fort 3, Reflex 9, Will 7.

As for XP, you have one total for all your levels. It doesn't matter what levels those are, just how many you have.

For example, a pound of fruit costs a certain price. It doesn't matter if that fruit is apples, oranges, or apples and oranges, only the weight matters.

Translating that into PF rules, an 11th level character on the medium XP track has 155k XP. It doesn't matter if he is a 10 Bard/1 Rogue, 6 Bard/5 Rogue, or 1 Bard/10 Rogue. 155k XP means 11th level, and only 11 separate levels.