You can pick up points on incidentals such as room service, restaurant, gift shop, etc, just so long as you bill the items to your room. You'd get 10 points per dollar spent so long as the amounts were credited to your folio.

You might also try a purchase or two from this link:

http://www.skymall.com/webapp/skysto...ott_points.jsp

Don't go directly to Skymall.com itself; you need to use a Marriott portal to get the points. Using these strategies, you should score the extra 850 points in pretty short order.