Presentation is everything, especially when you are trying to convince someone that your company is the only one that can solve their problem. You need your presentation to go as smoothly as possible and to show them that you are consummate professionals. This means that you need the presentation to be set up quickly, everything to be new, shiny, and working, and then the everything to be taken down quickly and as if it had never been there. You also need the presentation to show that you know what you are doing. There is no question that you need the best you can afford.
When it comes to an AV production company there are a number of issues that need to be covered. You have certain expectations, and those expectations need to be met. In order to make sure that those expectations are met it is important that you be aware of what you should be expecting; after all, it does not help the situation if you go into the situation with a false set of expectation. The first expectation is that the company is professional; that is the bedrock on which everything else rests. As long as that expectation is met everything else should work out fine.
The next issue is their equipment. An AV company lives or dies based on its equipment, and an AV company that does not have the newest and best equipment is probably going to die soon. This is not because old equipment is in and of itself a bad thing, but a company should always be upgrading and getting better; while there are some legitimate uses for older equipment, especially if you are expecting rough treatment, it is almost always best to use the newest and greatest. A company that does not use the newest should be held suspect; while old equipment has its time and place the newest allows options in case the user has to improvise.
The AV company also needs to offer a wide range of different services. A company with a range of skills is better able to handle any situation that comes up, sometimes being able to eliminate a problem before it even becomes a problem. By offering a tray of services rather than one or two a company shows that it is able to learn and overcome any problem rather being overwhelmed by circumstances, making it a company that deals with problems rather than is dealt in by them. Because of this do not be afraid to ask a few what-ifs, but do not get to into asking too many questions; an interview goes both ways, after all, and if you ask too many questions you come off as looking for the company to fail. Make sure that they can do the job required and you should be fine.
Last but not least the company has to be aware of time issues. This means that they need to answer any inquiries promptly, as well as arrive on time. They also need to be able to set it up and take it down as quickly as possible. Time is money, after all, and you should be worried about anyone that wastes either. The company you work with should be professional enough to recognize that your time is valuable, as is theirs, and so should work like they have a purpose.
In short, the AV production company you work with needs to be a group of professionals that you would like to work with again. They should be able to set up to necessary specifications, handle anything that comes up, and recognize that time is valuable. If you can find such a company holds on tight to it as they are worth it.