Here's a slide I thought had particular resonance.
Separate the idea from the execution.
We try and do this with the Post It Note thing, and it also references the 'Present Passion Not Perfection' idea. It's too easy for clients to reject work because of details, you know, the "I hate his green jumper" comment. Try and get the client to buy into the idea before you get into the details.
Tell them, again and again.
This is so important. Take a look at any great political speech. In fact, take a look at any political speech. Next time Bush talks about the 'War On Terror' count how many times he says 'freedom'.
Next time Gordon Brown makes a budget speech count how many times he says 'lowest interest rates for 40 years' or whatever his key theme is...
They're telling you again and again and again. It works (and they have difficult things to sell like tax rises and wars, not wacky print finishes).
Give them the tools to sell internally
Again, this is vital. Make things easy for your clients. Remember that most clients just want to get promoted. Help them achieve this and you'll be suitably rewarded.
Design your proposal so that it's easy for them to forward to their boss. Make it clear what the next steps are. Make it easy to sell your ideas.
(I hope you don't mind me putting these up here Jeffre?)