[antoinevg]

1. Not making it clear to the client up front that I'm charging for the week whether they have enrolled me in their IT systems or not!

2. Not making it clear to the client up front that if they wanted me to do the work the following week I've also have to charge them extra for having to reshuffle my schedule.

With big companies this stuff is very hard to fix after the fact, it has to be part of the initial negotiation.