The most common hiring strategy I’ve seen is when the hiring manager is looking for more people to do similar work to the work already in progress in the organization. For technical organizations, this means more developers/testers/writers/whomever with similar functional skills and the ability to easily learn the product domain.
When you have plenty of candidates, it’s ok to look at tools/technology skills. But if you don’t have lots of candidates, make sure you’re looking at how easy it is for people to apply their current functional skills to your tools/technology.
One common mistake I’ve seen, especially in smaller organizations growing quickly is to assume that you need all people at one level. If you consistently hire lots of senior people, you end up with a top-heavy organization. If you consistently hire lots of mid-level people, you end up with a bunch of people who are not able to progress to the top level (which might not be a big problem). If you hire only people with little or no experience, the manager has to take the time to coach them and help them grow technically and personally into responsible staff.
It’s critically important to do a job analysis for the first open position, and continue to re-evaluate the analysis as you hire more people.