One of the biggest problems with the personal training (and even strength and conditioning) industry is that it is more or less self-regulated. Meaning it's not particularly regulated at all. In fact, you don't legally need any sort of course or education to call yourself a personal trainer/strength coach, and this can lead to, at best, poor results for the client.
In an effort to help you see through this, I thought I'd offer some thoughts on our own hiring standards - after all, if we wouldn't hire them for our facility, why would you want to hire the cast-offs? (I should note - having the qualifications that I list below only get you the first interview; if you don't have the right personality, not amount of certifications or education will get you hired.)
Firstly, I ignore any "group fitness certifications" like bootcamps, spinning, and so on. You can pad your resume with these if you like, but I couldn't care less. Knowing how to manage a crowd is great, but it doesn't mean you have the slightest clue about how to coach movement and performance. And frankly, a DJ at some nightclub probably knows how to manipulate the energy of a room better.
I do look for a degree. Preferably in Kinesiology, though this is not the golden ring many people (potential clients, doctors, etc) seem to think it is. While it gives an individual a leg up, it doesn't guarantee they can apply, practically, any of the knowledge crammed in their heads. However, having any sort of degree does suggest a familiarity with academia and higher learning - so it's always a plus.
If someone doesn't have a degree in Kinesiology, I will then look for other credible certifications - and these can be counted on one hand. I expect to see a certification from the National Strength and Conditioning Association (NSCA), the American College of Sports Medicine (ACSM), the National Academy of Sports Medicine (NASM), and/or the Canadian Society for Exercise Physiology (CSEP). As a side note - a Kinesiology degree is a prerequisite for the CSEP certification.
There are a few other training backgrounds that I personally have experience with, and that will have extra credibility with me - however, they are not necessarily something the average potential client would need to know about. That being said, the above qualifications will at least give you a starting point to aid in narrowing the field if you are looking to hire someone; and also keep in mind that if they are easy to book in with and come at a lower cost than any of the others you've spoken to, there's probably a reason. A high price doesn't guarantee quality, but do you really want the lowest bidder with a wide-open schedule taking control of your movement and performance enhancement?