Lose 20lbs + Learn to ride up walls.
Or more seriously.......
Book somewhere to stay in Seascale NOW, unless you want to camp.
Don't rely on being able to take your bike on the train unless it's bagged up. This year there were about 20 people left on the platform at Lancaster cos the local train to Seascale only allows a couple of bikes (to be fair there were 4+ bikes on before they stopped any more).
It starts off stupidly hilly, has some more big hills in the middle and ends with some more steep bits - but don't worry the last 5 miles is downhill
Make sure you've done at least a couple of long hilly rides (60 - 100 miles) in the months going up to the event.
Unless you want a trip in a helicopter, go easy on the descents of Hardknott and Wrynose. They're silly steep and a long way from anywhere.
Enjoy it. It's a brilliant day out, and very well supplied/organised. I've done it the last 2years but I'm giving it a miss next year due to other commitments. I'll be back for 2016 though all being well.