You need to carry the stuff and have the ability to fix a puncture in either wheel and get it going again if its been underwater. Hopefully you wont need either but.....
Try get all your bits and bobs fixed to the bike so you arent carrying them.
A little extra juice stowed on the bike somewhere (if allowed?) can save a lot of pushing as some of the fuel stops can be near the limit for some of the modern bikes. A little luck goes a long way too. Remember its a marathon not a sprint cos its a long long way round!!
Good luck and above all enjoy the experience.
