Don't wait for a company to advertise they are hiring, because not all the time will they advertise. It is always better to interview for a job that is not listed, there is probably less competition.
You can look in newspapers, business publications, blogs etc Here are signs that the company is going to need more manpower. Look for the following signs:
Interviews For Information - If there are a few companies that you would really like to work for at some point, then find out the head of the department that you would like to work, then ask him if he would mind if you came down because you want to talk to them about their company''s, products, services etc. They might not have anything open at the moment, but they might be able to give you a few tips, and keep you in mind in the future if they do have a position open.
Contact Companies - Make a list of companies that you are interested in working for. Check their websites'' and or blogs'' . check to see if they are hiring. If there are no positions that fit your skills and/or requirements, then send them a letter, (not your resume), and ask if they are planing to hire any time in the near future, and if they mind if you could keep in touch with them.
Unemployed Support Group - Check your local area for a current unemployed support group in your area, if there is not a group then think about starting a group. There are quite a few advantages to do this, such as
Networking - Build a list of contacts that might be able to help get you a job. If you can create a list of names of various companies that you would like to work and try to befriend them via Facebook, Link In etc. If you do this do not just befriend them to get a job, befriend them to get to know them as people, remember friends help friends.