Generally, in my pre show crew roll call, I'll do a quick run down of how I'm going to work with the spots. Something like:
"Spots, your Act I frames are 1 & 4 (I only say this if they stay the same through the whole Act); take all entrance and XT pick ups and fade outs on your own; anything that comes up while the dancer is on stage, I will call for you - unless I tell you otherwise."
(they can see better than I can when the dancer is actually on stage and coming off stage)
Then in the show I give a long standby to give time to set the spots up, something like:
SB Spot 1 to p/u the Swan Queen entering L4, Spot 2 to pick up the Prince from R3, both frames 2 and 5, on a 5 ct.
(I don't have to say "on your own" because I already established that convention top of show).
Or,
"SB spot 1 to fade out on the prince and pick up the Queen, she'll be upstge left on the throne."
....
"Spot 1 to Queen GO"
(because the Queen is already on stage)
Sometimes you have to give a bit more explanation; like I would add "the swan queen will be one in the short white tutu with the crown, the prince will have white tights and a black jacket on."
My LD will sometimes do a Q sheet for them, but not always. He mostly gives everything to me and I just call it -- that way they don't need a Q sheet, I know where all the entrances and XTs are since I've been in rehearsal (unless of course we get to the theatre and they decide to change what wing they enter in!).
I think its important to work it out with your LD how much info you are giving the spots and how much info he/she will give them. And then its also important to make sure the spots understand who you are talking about -- remember that to them a character or actor/dancer name doesn't necessarily mean anything. On their first rehearsal you will probably have to be very descriptive and pick out some distintive points about who they're going ot be on, so they know who they have to pick up -- then once they know it, you can probably take the description down. E.G. at the first rehearsal with spots, you may want to be as descriptive as, "....p/u the King; he'll have a green jacket on and a big gold crown and will be standing DR"
Of course, if all the men on stage have green jackets and gold crowns, this won't be much help!
I recently had a situation where two dancers were dressed exactly the same and were standing next to each other when the spots had to pick them up -- at first I tried to explain it to the spots by saying where they were on stage, but that was still too confusing so I finally ended up doing it this way --
"Spot 1, your girl is entering on the ramp right now - keep an eye on her...Spot 2 -- your girl is entering on the ramp now -- keep an eye on her. These will be your next pick ups after you fade out on who you're on now."
I was able to do this b/c they were pretty skilled spot ops so they could multi task like that...but yikes! It took a couple rehearsals to finally get it right (I think maybe on opening night was the first time no dancer was left in the dark!
I think its mostly a matter of figuring out what makes the most sense to the spot ops -- they're the only ones that need to understand what you're talking about. Sometimes it helps to talk to them directly and figure out the best way to call something so they know what you're talking about.