Hi and welcome to the wonderful world of fostering! My husband and I have been fostering for about 6 years now and have helped over 100 dogs get to their forever homes. We stumbled on a fantastic group to work with, and have learned so much. We are a breed-specific rescue group (beagles), but I have lots of friends in the rescue community that foster for all-breed rescues as well. At some point you will think you must have been crazy for volunteering to do this, but it really does make such a difference.
Something that I think is very important is to make sure the group you are fostering with lines up with your beliefs and values, although if you are new to the fostering/rescue/adoption world you might not even know what those are yet.

For me, this would include things like a thorough screening process (we do a phone interview, vet check and home visit), spay/neuter before adoption (even puppies), inside dogs only, microchipping, etc...
As for experiences....wow.

Ours run the gamut from joyful to heartbreaking. We've done everything from whelping litters to hospice care, special needs, heartworm positive and various other medical issues. One of my most memorable is a little beagle girl who had blastomycosis (similar to histoplasmosis in people) whose owners moved and left her to die in a pen outside with no food or water. The inside of her mouth was caked with straw when she was found, because she had nothing else in her pen to try to eat.

She was skin and bones, it was horrifying and so, so sad. She was at the U of I hospital for four days in the ICU and took about six months to fully rehab. Eventually she was adopted by a fantastic family and is living the good life now.
Of course, most are not that dramatic. Most of them have just been in need of a little love, TLC, and soap. Some I would even say I was....more than ready to have them move on to their forever homes.

The thing about fostering is that not every dog is right for every family, and certainly every dog won't be right for *your* family, so your job is to figure out where he/she will fit best and help that dog find a permanent home. Obviously biting is non-negotiable since you have kids, but definitely expect things like potty-training issues and general bad manners like jumping or nipping. I really like the site ddfl.org for advice on things like that!
Okay, this turned into WAY longer of a post than I had intended, so sorry for that. Please feel free to PM me if you have any questions...sometimes this board makes me crazy so I don't hang out here much, just jumped on from the New Posts link.