I have a software product that may have some appeal to a relatively small, vertical market. I am considering hiring a salesperson part-time (which can be in addition to the salesperson's other work provided that there are no conflicts of interest) to sell this product, customizations to the product, etc. What should I look for in such a salesperson?
Given that it sounds like you yourself are not a sales subject matter expert, I'd try to find out if the candidate could explain the following:
a general process for doing sales - ie, how does one geneate leads, how does one go from initial intro to colosing a deal
what are some of the pitfalls and solutions to working in sales
what is particularly difficult in this area
what kind of strategy might work in your specific case
If the person can explain this stuff to you - in both a generic case and in reference to your specific product/needs - then you probably have a good one. I think this is particularly important in that if they can't explain to you what they are doing on your behalf, why and how they are doing it - then they aren't right for you. You're going to be a small team, so if you don't understand your sales person... how are you going to resolve problems?
This person is likely to share in the vision and help form how you sell your idea... so you have to be able to trust them, and that's a communication and chemistry thing as much as a knowledge/skill thing.
Also - you'll want to incorporate negotiation in - how can you and the salesperson swing a pay mechanism that you can affort which motivates the sales person without depriving the company of capital. There's all sorts of tradeoffs between salary, sales bonuses and other incentives.
in two words "people person".
I have a slightly different take on this. I think a good sales person is someone who is extremely friendly (but not overly), genuinely warm (but not slick), good at listening with intelligent replies. Great at forming instant personal relationships with folks and able to see and relate to their point of view.
They should be able to recount several stories where they're charm and personality won them success (and this can be outside of sales).
Other than this they should show knowledge of the industry they are in, a track record that reflects the level that you want them to be at for your requirements and price and good recommendations and references. A quick web search and review of their credentials shouldn't raise any red flag.
Just as with hiring for any other role, a track-record of doing this successfully and an enthusiasm for doing it here. It's worth thinking about though what responsibility this person would have for agreeing and specifying modifications, and whether they would deal with any contracts. These are skills that some but by no means all sales people have and you may well not want them executing contracts on your behalf.