Supply Teaching- getting work

Once you’ve made the decision, for whatever reason, to do supply teaching the most important question is how to actually get work? A quick google search will bring up any number of supply teaching agencies operating in your area but there is no guarantee that any of them will get you work. It would be tempting to sign up with all of them but this is would increase the amount of work you get and may actually be counterproductive. Agencies in a particular area tend to know each other and will soon suss out whether you are signed up with multiple agencies. Meaning they will contact those on their books who they know are more likely to be available rather than those who might not. ┬áSo how do you get more work?