[timwaagh]

make sure they are easy to get rid of (don't contract them for a fixed time period) or consider working with an established it consultancy. they will do the vetting mostly for you. it's perhaps a bit more expensive, but rates are still competitive and the one who loses most from it is the contracted consultant, as most of his pay goes to the consultancy. as for fixed fees, im not a fan as situations change so it tends to lead to conflicts.