This is for moms who are freelance writers/work on writing part-time. I did that for 3 years before returning to full-time work 2 years back. Now I'm considering going back, but want to approach it differently. My question is: how did you build your network of clients? I could always go back to my old ones but I would like new clients and different work to do (and hopefully get paid more). :)

Well, I had a few friends/former teachers in active journalism so I started out with a few articles in weekly supplements. Then I got a big writing project for a non-profit organization, again, through an old professor of mine. I also kept a lookout for freelancer work on job sites and that's the one that got me a regular writing gig. The pay was good because we were writing in India for clients in the US, UK, and Australia. In the meantime, other work poured in from former clients. I was fortunate to not have to ever really look for work. In around a year's time, I ended up having to turn down work because I had enough and more on my plate.
I never had an unsatisfied client because I spent a whole lot of time understanding exactly what they wanted and insisting on regular feedback for projects lasting more than a week. One client eventually told me: I stick with you because you work hard and are open to my ideas and accommodate last-minute changes. (sorry to be blowing my own trumpet.)
I had one nasty experience with a large multinational corporation, after which I learned never to work without a contract in writing. An email from an official ID is enough, but you need to have something. There are good clients and bad clients, and after a while, you learn to go with your gut. There are a couple of projects I turned down because I was simply not comfortable with the way the client was approaching it. And from what I heard later, those clients turned out to be nightmares for the people who took up their work.
On another note, you could join networks of writers that help each other. There's one called Informed Ideas for Writers on ning.com. It's fairly new but has plenty of good resources. All the best.