Rule #1 in private protection work: no would-be martyrs or saviors need apply! That sort of thing is strictly out of the potboiler novels.
For the past 7 years, I've been working as a security receptionist officer for a large international private protection firm, and for several years I worked as a production assistant at a small market TV station where I had de facto security & bodyguarding duties for the anchors/reporters. When I was in the USMC, I served guard duty on several occasions. On all three jobs, I've have been fortunate enough to meet several VIPS...this includes CEOS, high ranking officers and some big name celebrities. I personally find security/private protection a very rewarding career.
However, you should know that security work in any capacity is not the most glamorous work in the world. The turnover is very high. The pay and benefits are not always the best. Some places are union, most are not.
You'll have to work weird hours, be on call, and there will be assignments that can be very boring! Your first few jobs will probably be pretty mundane....and sometimes it can just be a downright sh*tty "go-fer" job where people will look their nose down and not even say hello to you. However, there will be times when you'll suddenly become "everybody's best friend" especially if they're trying to pump you for information or get past you without credentials to get close to that VIP or celebrity.
So it's essential that a security officer in executive protection is able to possess a thick skin, have the ability to be impartial while on the job and do it while remaining friendly and courteous. Some jobs will require you to play the "heavy" to the hilt...uniforms, guns and all, others you'll need to be able to blend into the background and be part of the crowd...so flexibility is important, too.
You have to work your way up to guarding the individual VIPs or celebrities. MOST people involved in executive protection have YEARS of experience in the field...and they are screened beforehand to ensure that they are true professionals... NOT criminals, psychos or simply starstruck.
Even if you get to that level, it is NOT guaranteed that you'll be assigned to any specific celeb...so don't ask! It's considered very unprofessional to do that, and if it's discovered you're a "big fan" of celebrity X, then that will more than likely include you OUT of the running for the job. If the celebrity or their handler is interested in you for employment, then they will select you through your agency, not the other way around.
Most celebrities do not appreciate familiarity on the part of those who are employed by them in any capacity...and if you're interested in trying to get a job with a celebrity with the hope of becoming a celebrity yourself...fuhgeddaboutit! There's only room for ONE ego...and guess what? It's not about you!
The ability to be alert, discreet, and respect confidentiality is very important for a successful career in executive protection. You might even have to sign a confidentiality/nondisclosure agreement as part of the job. This means you don't talk to tabloids or friends about what you hear or see, nor do you write a book about your experiences about your tenure on the job. Some celebrities make employers sign an agreement that says you will not have unnecessary contact with the celebrity...i.e. talk to them about non-business oriented things on or off duty. Some don't even allow eye contact, believe it or not! On the other hand, some celebs have been known to treat their security staff as BFF and in some cases even get romantically involved (not really a good idea IMO)...it all depends on who you work for.
Ok, if I've not scared you off and you're still serious about getting into this sort of work, then you'll need to complete the requirements in obtaining a Guard Card for your respective state, and then contact bona fide security agencies for employment. Just enter your state name and guard card in a search engine and you'll find the information. Requirements vary from state to state.
Opportunities for executive protection jobs are available worldwide. However, California is where most celebrities live and do business, so here's more info for that state:
A few of the larger national or international security companies that specialize in event security or executive/celebrity/VIP protective services include Wackenhut, Securitas, and About Force...and there are lots of smaller independent companies too. If you put "executive protection celebrity bodyguard" in a search engine, the various agency websites will come up.
Some of the companies will help you get a guard card and provide the courses you need. Others will expect you to already have those things...as well as appropriate experience.
For most security jobs, you'll need to be at least 18, and be able to pass a drug screen. They'll also do a thorough psychological and criminal background check on you, too...at least the reputable companies will. There'll be additional requirements if you're to handle any sort of firearms. Some places will also do credit checks, too. If your specific job requires any sort of international travel, you may also need to get a passport.
Best of luck if you still choose to go into this field.