First you must have a 4-year undergraduate degree. This degree is usually in psychology, but some institutions will accept degrees in behavioral science, sociology, etc. You should do a thesis, as most schools do require it for academic advancement. You must next get a masters degree. This is typically a 2-year program.
Many people work with just a masters degree.
One major area of specialization is psychometric testing. However, a PhD will always find it easier to get employment. They will also be paid more. It doesn't really matter at the undergraduate level. The key thing to look for is how the program is compared to other schools.