An interesting article on ERE.net discusses the qualities that help workers successfully work from home on "virtual teams." While the article is addressed mainly to employers, recruiters placing candidates who will be allowed or required to work on projects from home, possibly on a contract basis, can gain some helpful insight from this article as well.
The main point of the article is that telecommuting requires different skills than performing the same work at the office. So if you are recruiting for a direct or contract position in which most of the work will be performed at the worker's home, you may want to look for candidates with the following qualities and skills:
Of course, the best candidates for remote work will be those who have telecommuted in the past, but hopefully the qualities listed above will help guide you when experienced telecommuters aren't available.