I started by looking on Facebook for day home groups to join! there were lots of parents sourcing these groups for child care. I also call the city to see if they had a registry that I could be added to. this worked as well, they just gave me some forms to fill out and a little about what I offer for care, my experience and police checks. this website is good for advertising as well!
The other thing I did was approached the schools near by and asked if I was able to put an ad up on their bulletin board! some do, and some don't. I also went to the nearest recreation center in my area and posted ads on their bulletin boards as well. there are a lot of places that will let you put an ad up, just have to ask....Don't be afraid to put yourself out there!