1. The dispatcher should be a matchmaker. This means that this person knows your customers' personalities and their equipment as well as the capabilities of the technicians. For new dispatchers this can take time to learn. However, your computer system can help with history and equipment lists. Your dispatcher can and should learn the different types of equipment and the approximate age of each of the pieces of equipment.
By matching the right technician to the right job you'll have less callbacks and less unhappy customers. An expert in condensing units won't be sent to a heat pump call. Or an expert on 20-ton rooftop units won't be sent to a chiller call. A "chatty" customer won't be sent a technician who hates to talk.
You've all had situations where a newer technician didn't fix the system right but took care of the customer. The customer calls and says, "The system still isn't working, but it's OK" in a nice tone of voice. There have been other situations where your best technician hated talking to a customer fixes the system and the customer is unhappy - not because the system is fixed but because she was not treated right (from her perspective, which is the one that counts).
2. Keep the technicians in the same area whenever possible. And, for residential work, dispatch from home. You'll save on travel time and get more billable hours per day. Even if commercial customers are paying for the travel time, they appreciate that travel time being as short as possible.
3. Call the customers before you send a technician to their home or office. This goes for commercial work too! From a residential perspective, you want to make sure the customer is home so that you can do the work. From a commercial perspective, you know that the customer will be there. However, this is a courtesy call which will separate you from the rest of your competition. One of the contractors I worked with got a letter from a commercial customer thanking them for always calling even though they realized that they didn't have to call.
4. Leave the second call of the day open. This means that there is enough room for when "Murphy's Law" strikes during busy times. If you can't fill the slot with an emergency (and you almost always do), then you can always move someone up. I don't know very many people who wouldn't like you to get to their home or office earlier than you had planned.
5. Debrief the technicians before you give him or her the next call. Get model and serial numbers, customer signatures, store stamps, etc. that you need beforehand. That way you know that you have the best chance of getting everything you need so that you won't have to go back.