For me:
1) Scrunch the quilt into the harp, don't roll
2) Start in the middle and work out in quadrants.
3) Make sure to have a table behind your machine to catch the quilt (at least 3 feet wide) and a lot of space on your left to hold the quilt up. You want as little drag as possible.
Also- DSM means a lot of different machine sizes. Some have very very tiny harps. I have a Bernina 430 and can do it, but when I had my Brother XL-3010 or Kenmore 16221, I don't think there would have been enough space.
Leah Day has a fabulous video about quilting a king on a DSM (a few actually), but she uses an extended harp DSM. She uses either the Juki or the Janome that are made with a lot of extra space.