I was very worried about this when I started volunteering at my shelter, then working for the vet hospital also!!

Be sure to keep some "crap clothes" around to wear everytime you go to the shelter, and shoes too. You never know what kind of "fluids" you may encounter while volunteering. I dealt with urine, some blood, vomit etc...but I also helped with the sick animals at the shelter a lot, so depending on what sorts of things you will be doing will help determine your garb.
Whenever I came home, I left my shoes outside, and like kuhio98 said, went straight to the shower, dumping my clothes in the hamper along the way whenever I came home.

I never had any trouble with any of my kitties, so I'm confident things will be ok for you and your furkids. It's a very worthwhile endeaver and you will feel so great for helping these precious babies at the shelter.

**hugs**
Karen