I've noticed lately that a number of organizations in the IT industry, searching for a project manager, are making experience in working with specific software a requirement. First let me say that I have nothing against organizations hiring project managers looking for specific skill sets. "The customer is always right" in the area of resource acquisition as well as in the retail trade. If experience in use of a certain software product is really important to you then by all means make it one of the selection criteria. My point is that it should not be assigned the same priority as some of the other selection criteria.
To successfully manage a software project, the project manager must have a solid grounding in general project management practices. These practices are fairly thoroughly covered in the PMBOK® (Project Management Body of Knowledge) and any project manager who has demonstrated their grasp of these practices by passing the PMP® certification exam can be relied upon to use them to manage your project. The fact that a project manager has been certified as a PMP® should not be used as the only hiring criteria and it should not be taken as a form of performance guarantee. It is merely an indication that the certified project manager has studied project management best practices and is able to demonstrate an ability to use them in project situations. Those looking to engage a project manager should not choose a project manager simply because they have the PMP® certification unless they are able to demonstrate an ability to manage their project to a successful conclusion.
I'm suggesting a top down (or bottom up, depending on your stance) approach to identifying the skills and experience that will identify the ideal project manager to you, with the top level representing the higher priority criteria. The demonstrated ability to use general project management practices should be your highest priority. Certification of a project manager means that they have a command of these best practices and can identify them with simulated project problems in an exam setting. You should look at the project manager's experience as a means of demonstrating the candidate has used the best practices to successfully manage projects. If you are working with selection criteria grouped in "must have", "important", and "nice to have" categories, general project management skills would be a "must have".
The next most important criteria will be the ability to manage the project's human resources to successfully deliver the projects they have managed. Again, this ability should be demonstrated by the candidates experience in managing similar resources on similar projects. I would argue that it really is not necessary to have managed a specific type of resource (e.g. database architect, C++ programmer/analyst, etc.) in order to demonstrate the ability you need. Look, instead, for the candidate to demonstrate their ability to create and maintain a high performance team, then look for a demonstration that team was able to deliver performance above and beyond the sum of its parts. A project manager with zero experience in managing a C++ programmer, but who has had years of experience in developing high performing software development teams is much more likely to deliver the results you need than one with experience in the management of that specific resource but without experience in developing high performance teams.
A project manager's experience in managing projects of a similar, or greater, size and complexity than the one you are undertaking is the next most important criteria on your list. Look for project complexity indicators such as the size of the project teams, the number of sub-projects, the number of applications and databases, the volume of data, the number of stakeholders, the budget, the number of customers or clients, and the number of vendors as indicators of the size and complexity of the projects the candidate has managed. The type of project and the type of software tools used in its execution matter less than the candidate's experience with large and complex projects. The project manager with a depth of experience in managing projects larger and more complex than yours will be able to take the added complexity factor of the technology (if indeed there is one) in their stride.
Your project manager will be the face of the project. This frequently means that they will be called upon to communicate with executives on a Steering Committee, or other stakeholder body. The project manager you select should be able to demonstrate the ability to identify the information needs of these stakeholders and the ability to meet those needs. They also need to demonstrate an ability to communicate with executives one on one, by means of presentations, or by e-mail. Smaller projects with lower profiles may not call for a PM with this experience. The demonstrated ability to communicate with executives and meet their information expectations is actually addressed in the scope management and communications management areas of general project management skills, but candidates should be able to demonstrate experience in dealing with this type of stakeholder where required.
Your project manager should also be able to demonstrate an ability to spot potential problems and issues before they impact the project. This is typically demonstrated by their experience with risk management. This is actually a general project management competency, but you may want to segregate it from other general PM competencies if your project is large and complex. Their experience should cover all risk management processes from risk identification to retirement of risks. I have also noticed some companies asking for PMs who have experience in "escalating issues". This usually means the ability of the project manager to spot a problem which the PM is not able to resolve on their own and reflects the desire of the sponsor to be informed of the issue in time for them to take action and avoid a negative impact on the project. This is actually covered in the Communications Management area of project management best practices, but you should ask the candidate to demonstrate their experience with managing this area of project communications.
The last item on your list, and the one with the lowest priority, should be the candidate's experience with the technology chosen for the project. I would actually recommend deferring a decision on technology until the PM has been chosen, if at all possible. Too many projects are hampered by a decision to use a technology that has been sold to the executive sponsor or IT sponsor, without consideration for what will best meet the project's needs. Choosing a technology that the project team is comfortable with is also a consideration. For projects that must utilize technologies already in place, by all means choose a PM who can manage a project using that technology. Making this criteria the lowest priority means that only when you have two candidates who have met all the other criteria equally well would this be a deciding factor. Hiring organizations who have the luxury of choosing from among two or more candidates capable of demonstrating competencies in all the other areas I've mentioned should consider themselves extremely fortunate. Providing you've done your due diligence in the interview to ensure the candidate actually has the experience they claim, you can't make a bad choice!
Hiring organizations should be prepared to do some leg-work when they engage a project manager. The amount of leg-work will be commensurate with the importance of the project to you. Selection of the project manager who will take responsibility for a project that is critical to your organization's strategic plans should not be the result of an automated search for a key word or phrase in a resume such as C++, Agile, or Oracle Version 10.1. The temptation to use these key words and phrases to limit the number of resumes you have to read through is strong, but try to resist it. The reward for this extra effort will be the rich field of candidates you have to select from. Using the same care and discipline you would use when selecting a vendor for a million dollar contract will pay off by identifying the best candidate and increase the probability of a successful delivery of your project.