This is something I know a lot about as it happens to me all the time. On the flat I'm fine, but even the smallest incline and I'm being shot out the back.

Now, they always say you should practise what you preech and I'm own up now and say that, as yet, I haven't done this, but practically everyone I talk to tells me this is the best way to respond to changes in pace, or times when you need to increase your effort - eg when the road starts to roll. In a word - intervals.

If you're not familiar with how these work there's plenty of literature around on the subject, and I'm sure there's plenty of people out there who can give you a more detailed description than this, but it basically involves a short period of intensive effort, followed by a short recovery, then repeat. For example :

1 minute max effort on -
1 minute recovery
2 mins on
2 mins recovery and so on

By the way this is just a very crude idea of how they work. You can vary it a lot , for example increasing time 'on' and gradually reducing recovery time.

The idea behind this is you train your body to respond to sudden changes in pace - eg sprinting up a hill, jumping on someones wheel who might be going for a break etc. It also greatly improves your recovery time.

I'm sure the mtb riders will put me right on this but I think a good lumpy mtb ride, where you have a lot of changes of pace would have a similar effect.