I'm 12 years and I NEED a babysitting job. I am responsible and I LOOOOOOOOOOOVE kids

Put signs up all over town. Full size paper for telephone poles and maybe 1/4 size ones for stores and bulletin boards. Print them on your printer if you have one. If you can afford an ad in your local paper, put in the minimum number of words. A stapler opened flat is best for putting up but bring tape too for metal.
Don't put your name in it, and let a parent answer the phone in case of crank or suspicious calls.

I agree with Joy--great ideas by the way!! I would see if the local daycare centers would post couple of your posters. Even church bullentins.