Security Agency - What should be the best criteria to hire a security agency

Private Security agencies are growing like Mushrooms in India.Security guarding services provided by various agencies have numerous problems in respect of their performances. Operations, manpower, Compliance and training etc.One of the very important fact I come across is that police verification of security guards proves to be challenge for security agencies, especially so when these people come from other states and do not have valid address proofs etc.In the shadow of such issues, Clients, looking out for a competent security agency becomes a difficult.
Having said these,I request to know that How the bset criteria can be set for hiring right agency and how the performance of the agency is to be tracked to get best out of them.

Dear Bijay,
I can understand your concern, but there are may security agencies are there in the market which follows all the compliance's and provide guards with all formalities. The good company can be traced with their past performance in the market. Also, feedback can be taken from client list that they have about their performance and compliance following attitude. While searching for correct fit agency you need to see if the agency is following all the legal compliance or not along with TAT they normally take to replace the guard in case of requirement and more importantly all security guards should be on duty shall be allow only with police verification. All these details can be found out with market survey.

Thanks Mr. Manoj,
Agreed to your points.However I find clients always do have one or the other problems with security operations with agencies.How this can be improved upon?What roles can be played by those who need security services and how the agencies can contribute to improve the standards of security services industry.