Just as a salesperson should always be prospecting, a sales manager should continually be recruiting, even when there is no open position. At a trade show, he should be talking to the salespeople at the other booths. He should have a recruiting file and always have a list of possible candidates. He should always be evaluating his sales team - identifying the weakest performer(s) so they can be replaced with stronger people.
Determining what you're looking for in salespeople is the most important step in the recruiting process. I believe this is best approached by simply considering your services and products, and the customers who your salespeople are expected to sell. Make sure potential salespeople have experience calling on that particular type of entity, whether it's government institutions, corporations, homeowners, etc. Will they call on the president, human resources, IT or technical end users? What is your price compared with your competition? Do candidates have experience selling at the highest price, average price or lowest price? What is the average price of a sale? If you need someone to sell million dollar contracts, one will likely be uncomfortable if they have previously sold significantly lower tickets. Do customers buy the product once, or is it a continuous process? Are the salespeople going to be the hunter-killers and simply bring in the account and turn it over to a customer service group, or are they going to have to service the account? How much cold calling will they to have to do? What's the minimal product or technical knowledge they need to have?
Identify the selling situation, and have an idea of the kind of values that are most important in that situation. For example, if you need a salesperson to develop a new territory, you want that person to be highly utilitarian, with a strong need for significant return on investment, and individualistic - a self-starter who makes things happen. Look at the behavior patterns of your top performers and try to match them.
When reviewing resumes, examine the flow of a candidate’s resume. Has one been in the same position for ten years, or do you see a pattern of growth? If you see a lot of lateral moves, it's a signal that maybe this person is not such a high flyer. You want to see a progression of moving forward.
As always, the number one predictor of future success is past success. Successful people will continue to be successful people. Salespeople who have made their quotas for the past five or ten years will continue to make quota.