I applied through college or university. The process took 1 day. I interviewed at UC Merced (Merced, CA) in Jan 2014
Interview
10 minutes interview and present something.
The interviewer will have some questions based on your presentation.Several students will also have some questions to ask. The whole process will last 20 minutes
Interview questions [1]
Question 1
present something and knowledge which you are familiar with
There will be three parts for the teaching assistant interview. First is self introduction, second is to repeat a syllabus they provide to you, and the third part is to give a mini-class, using any topics you like.
I applied online. I interviewed at UC Merced in Feb 2013
Interview
Hiring is based on whether or not you are accepted into the program, a research group, and faculty's lab. Once that's taken care of, you're in the system. They'll guarantee funding and positions. It's really a sweet deal.