Wrap yourself in bubble wrap for the 1st few rides just in case you topple over at the lights.
Practice clipping in at home by riding up and down the the garden path then accidently on to the flower bed.
Remember that traffic lights will always go red when your 5 metres away from them so be prepared to fall over/lean against a barrier or car. Anticipation is the key here.
Walk around your local high street in your new cycling shoes so you get used to the funny looks everyone will give you. This comes in handy when you have to make an emergency shop at your LBS.
Finally dont wear them if your planning on getting a fast start at Palace as you'll fail to clip in and be at the back before you can say SPD....as I found out 2 weeks ago.
Hope that doesn't help and Ive made myself sound stoopid.