What has worked well for me in the past is having a tune where the start of the dance can happen every two bars or so (in other words, a tune that is not harmonically complicated).  Making walkthrough prompts in time with the music, but not giving a particular set amount of time to each call seems to work well.  Dances that end with a move that can be extended (allemande, swing, etc) can help sync if you need that extra beat or two.  I've found that rolling starts work well with a dance that starts with a balance, as that can make it very clear where the dance starts.  Otherwise, asking the band for four soft potatoes at the end of the rolling start can be helpful.

Hope that helps!

-Dave