When tuning drones do I tune to D on the chanter or A on the chanter?
I don’t know about anyone else, but I tune relative to the A, F G and both D’s. I’m not sure how scientific it is, but it seems to get them closest in the end 
However, I’m only just starting with these monkeys, so …
Try tuning the tenor drone to the A on the chanter and also check it against the G on the chanter.
Then shut off the chanter and tune the barritone drone to the tenor drone.
Then tune the bass drone to the tenor drone.
go here http://homepage.eircom.net/~robertscharles/ and follow the links
Jim’s advice is good. When tuning the tenor drone to the chanter, I make sure to check it against…well, all of the notes of the scale, but especially A (both octaves) G (both octaves) F#(both octaves), E (both octaves) D (both octaves)…You get the idea. A, F#, and D are probably the easiest notes to tell if the drone’s in tune or not. If the drone is not in tune, it will clearly make a wobbling WAWAWAWAWAWAWAWAWA sound. As you get closer to being in tune, it will become more steady (e.g. WA…WA…Whhhhum…) until it hums perfectly in tune with the chanter/other drones. If the drone hums in tune with the As and Ds but still wobbles on say, the F# for instance, that means the F# on your chanter is out of tune. In theory, if your chanter is in fact in tune with itself and you are able to play it with steady pressure over the full two octaves, you should not hear any wobbling of the drones against any note in the scale. In practice, there are probably few chanters that even on a good day and in the hands of an expert player are 100% in tune with themselves–the 2nd octave E or the 1st octave B might be a hair flat, for example. If your Ds, As, and F#s are well in tune though, that’s a good start.
I keep thinking of more things that could be added here. One more is to do a final check of all the drones playing together against the chanter. Especially when you’re first beginning to play with drones, one common error is that it can be easy to play the drones at a different pressure than you would the chanter & drones together.
It is maybe good to remember the A and G are the first notes to change, go flat when the reed opens and sharp when it closes, with changes in temperature and or humidity.
It’s a series of compromises…
on a good day, there’s a sweet spot in the middle where the drones phase-lock and the chanter fits right in and it sounds perfect. Even though it’s not 
thankyou gentlemen for your help.i am a little bit wiser now.
I have a D tuning fork that I use to tune the drones.