I have attended a 40hr APCO PST-1 class where someone who was not a desk officer or dispatcher was sponsored by a a police department for the purpose of gaining experience and adding to their resumé. Each department receives grant money each year to pay the costs for the course itself and to pay for any other staff members who may have to take the trainee's place on the desk that day. If you have a department that has leftover grant money, they may be willing to do this. Especially if that person may one day apply to become a dispatcher.
http://www.mass.gov/e911 is where you may find some of these courses. The 40-hr APCO PST-1 class is a pretty good course for learning how to handle different calls, questions to ask 9-1-1 callers, etc. Also as GMass mentioned... EMD is great as Mass. now requires, whenever practical, dispatch centers to provide/offer access to Emergency Medical Instructions via phone. The only thing you should look out for is that there are a few different EMD courses that a department requires. I know a dispatcher who has a APCO EMD certification for one department who had to be trained in PowerPhone EMD for another.
While i'm on it, along with EMD you'll need a CPR certification for First Responders/Healthcare Providers too.
Good luck!!
