First you must decide what area you want to work. Auto, appliance repair, two way radio, marine, medical, aircraft, railroad etc. They are all different. All have advantages and disadvantages. From there go to your yellow pages/internet and find some prospects. Don't bother to mail a resume, knock on doors. Many prospective employers will be small operations, they typically will not advertise. With today's economy they can't afford to spend time wading through ten thousand resumes.
Check with friends of parents, relatives, minister. These people know who is hiring, and can give you an inside track. If your parents have a friend who is in Rotary, LIONS, Moose etc, these are also good places to prospect. Finally, join the Reserves, CG or Navy (can't tell you about the other branches) have excellent programs, and will give you additional training, knowledge and people.
Best