I've been a TA for 3 years and it can be a trip sometimes. I remember at first thinking "what the hell am I doing? I am their same age!" So, I thought I had to maintain some sort of distance between me and them so I was really arrogant hardass all the time. That didn't work.
It's hard to be a TA and take classes sometimes because you are under so much stress in your daily life and you ask yourself, "why cant my students do this simple thing? why do they complain about homework? they don't know what homework is!" But then you have to realize that there is a huge difference between you and them and you don't have to be a dick in order to get respect, all you have to do is relate to them. You have to go to where they are. Most of the undergrads that you will be teaching are fresh out of high school, so most of them are semi-expecting something like a high school teacher, who is more mommy-esque. It goes without saying that no one here is fresh out of high school and has noted the difference in maturity between a high schooler and an upperclassman.
In the end, you have to teach undergrads as though they are children, but with more respect. It sounds condescending, but it's better to think this than to think that you are on the same level as them, because you are not. Your BA will be like kindergarten compared to your MA program in most cases, and most of your students will not be going on to a MA or even graduate with their BA, so don't get angry with them to be studious and diligent like you, just give them the grade they deserve and move on.
Also, I learned that it helps that if they ask how old you are, lie. Say that you are older than you are. It makes a world of difference sometimes.