The biggest mistake you can make is to become disheartened after rejection. Few find jobs on their first try. The best place to look is with people you already know. Visit or call people you know who work in your preferred area.
Visits are best and require appointments.
Explain that you are looking for work, what you want, and ask if they know of openings. Don't ask for a job. You're looking for referrals. If they have a job, let them tell you. Give them a brief background of your experience.