Job opportunities are more plentiful than in the security industry than other industries because of the phenominal growth. It is probably best to seek direct employment rather than working for an agency since you are more likely to work fulltime.
Keep your resume updated and do not exaggerate or lie -- you must be above reproach if you want to be in a position to monitor other people's honesty.
Honesty is not just the best policy, it is the only policy.
Always keep your appearance clean and neat. When you go for interviews it is very important to appear ready to go to work immediately. Answer questions carefully and always be truthful, even if the answer is not what the interviwer wants. It is better to pass up a job that is not right for you than to attempt to fool the interviewer.
123getajob.com/ -- free
smarthunt.com/ -- free
directory.co.uk/Security_Guard_Resumes.htm -- U.K.
Also: Career Prospects project, located at the Demographics & Workforce Section, Weldon Cooper Center, University of Virginia, PO Box 400206 Charlottesville, VA 22904-4206.