Most sales also offer 1 guest pass for the pre-sale per consignor. You can also pass the word at church or civic functions. You could also take out small classified ads in local papers. You need to decide what your portion of the profit will be. Some are more or less than that.
Most sales have a name that reflects previously owned children's items.
You may or may not want to name your sale. Others only advertise as children's or kid's consignment sales. Unless you have a small sale you will need recruit people to help check out, place items on racks, place signs for advertisement, etc. People sign up to help in exchange for even earlier shopping privileges. This is a very cost effective way to obtain help.