How to choose fontstacks

Im in the process of learning slicing methods from PSD to HTML and ive run into a bit of a hurdle.

Whats the best way to choose a css fontstack to match that from the PSD?

Is there a function in Photoshop that spits out something?

Can anyone give me a bit of advice how they choose which one to choose, and also, in photoshop it seems the text is taken by PT ... im using PX in my CSS, is there a way to change photoshop to display px instead of pt?

Thanks all :)

In Photoshop (on Mac OS X) go to Photoshop -> Preferences -> Units & Rulers. Under the "Units" section change the "Type" drop down from "points" to "pixels".

Here are two good articles with several font stacks:
Better CSS Font Stacks
Revised Font Stack