A great way to gage the technical expertise of a prospective IT partner is find out what systems the given company runs in-house. If they are running modern systems such as Windows 8 and Mac OS X Mountain Lion this will give an indication of what systems they support. If they run older systems such as Windows XP in-house then this should be a warning sign about the technical competency.
Another thing to research is how a company feels about cloud computing services. These are the future and also relevant to most business today to at least some degree. If the company is confident about leveraging cloud computing and online services to minimise the servers your business needs to purchase then this is a positive sign.