CL=Craigs List. Small businesses will often advertise for part time help there because it's free. So, for example if I see 2 people wanting a part time accountant, 1 person wanting a basic hr person part time, and someone to handle their e-mails for them a few hours a week, then I would e-mail them a letter explaining my services, the fees, and how it works (assuming I could do those jobs).
So here's how it works. Once you decide that you want to do this, you need to spend a little cash. It's usually not much at all mind you. Get a company name - it could be something like Jane Doe Virtual Assistant Services or something more creative, doesn't really matter. If you're not using your name as the company name, file a dba (doing business as) form with the state. When I lived in MO this ran $7 if I recall, though I believe it varies by state. Get some business cards printed up, a website put up, an 800# and a few brochures printed out (you can do those at home or at someplace like Kinko's for cheap - especially if they're only one color). Now, if you go through VistaPrint, you can get the business cards for dirt cheap AND I know they offer inexpensive websites to coordinate with their products. So maybe $30 there? Not sure but I seem to recall they were cheap on the website. Now for the phone number, that depends on where you are and what you need. You DO want to be able to take business calls on the line, so a home line with the message "You've reached Don and Sue" probably isn't the best idea. You can use a cell phone, a second phone line, or get a designated 800#. I use a company called UReach which I've been happy with for about $15/month. Total upfront investment to start your own business= about $80. And really all of this isn't mandatory, but it does give you a more professional air! (Tip: get the 800# BEFORE you order or print business cards. It sucks to have to redo them!)
For me personally, I'm not overly skilled in accounting though I can certainly manage basic bookkeeping. I am skilled in things like editing and web design and development. So I picked the catagory of Real Estate (because usually most smaller offices have to do everything themselves with no corporate support) and sent out about 30 letters. I introduced myself, explained what a VA was, explained what I could help them with, how I could save them money, etc. I also found jobs by posting my business on the local papers business site and on CraigsList. Some jobs are a one time deal, some are longer term so figure out what your pricing will be for each. But remember that people talk, and if one person is happy with you they'll tell their friends. Oh and while there is at least one legitimate organization out there (I *think* it's the ivaa.org) don't ever pay for job leads through any company claiming to do the middle work (unless it's something like guru.com - I know they're legit). I can't tell you how many complaints I heard about those companies when I was doing it!
It's not a get rich quick scheme, and it's not some type of marketing sales deal like Avon or Pampered Chef. This is you and only you. But there are some resources and support out there, and it can definitely work!
ETA: If you do decide to give this a try, never say you're "working from home" but rather present it that you're saving them money by working from your office rather than theirs!