Make sure that you always keep them in the loop.
Have the principals involved during preproduction meetings. They often have invaluable insights and/ suggestions.
Do proper tech location checks/run-throughs - check wireless lav placement on wardrobe, check to be sure there is sufficient power at locations, etc., etc., etc.
Do wardrobe and hair & make-up tests, with camera and lighting.
Preproduce the freakin' hell out of your production - the more thorough your preparations the less time is wasted on the set, and the time of your cast and crew is valuable.
Once you are on-set make sure that the craft table is well stocked all day. Good stuff, too!
Serve real meals; I'm so frigging sick of pizza and six-foot subs.
Make sure that there are clean bathrooms, and a comfortable place to hang out when not needed on the set.
Make sure that EVERYONE, down to the last PA, has a script.
Make sure that EVERYONE gets updated schedules. (This goes back to keep them in the loop.)
The concept is let every single member of the cast and crew know that they are important to the production and to treat them that way. People who feel that they matter to the production and who are treated well will work hard for you. Be thoroughly professional in your production methods and your habits/attitudes; it's always a pleasure to work with a real professional.