1-Always check whether the person has a license. While this is a necessity for many states, you should do your own research and ask to see a copy of his or her license.
2-Carefully consider the contract. It should state in writing exactly what services you expect them to undertake and what their fees are for such services. You do not want any surprises.
3-If you are looking at private investigators that charge hourly rates (as many of them do), ask for an estimate on how many hours they will devote to your case.
4- Many private detectives will be referred to you from past clients. After all, an investigator with little real-life experience might not be the best for your case.There are some instances where confidentiality may preclude them from sharing this, but still ask for past experience in your sort of case. Ask them for examples of outcomes and ask them to be as specific as they possibly can.
5-Ask to see their liability insurance and proof of bonding. If the detective happens to damage anyone’s property while on your case, you do not want to be liable. If they have insurance, look over their coverage , a million dollar policy coverage is beneficial to both you and the Agency he or she represents.
6- Search the Internet for reviews of the detective and or Agency
7- Check with the Better Business Bureau to see past history and if anyone has ever filed a complaint.
8- Do they have an office, or do they work out of their home? Many Private investigation firms that are run out of a home, can be an indication that they may not be 100% committed to this line of work.
9- Ask about equipment. Do they have large telephoto equipment ( 1300 zoom lenses ) ? Do they have 60x zoom video equipment? Do they have parabolic listening devices? Do they have cameras and video equipment that work inside low light areas? Do they have night vision video and photography equipment. All of these are important in getting quality admissible evidence for your case.
10- Have any grievances been filed with your state licensing division with regard to the agency or the operative themselves?