Being well prepared is half the work, you don’t have to do a full reconnaissance on the climb but you should be able to find out a lot of information from the internet. Many pro teams will use google earth to analyse the final kilometres of a climb. Try to figure out how long the climb is so you can properly gauge your effort. With a climb it is important to not give it your all at the bottom. Your goal will be that you go as fast or faster at the end as at the beginning. The best thing to do with climbs is to ride around your threshold zone. Keep a good rhythm with a cadence around the 80/90 per minute. Not a big ring as this will cost a lot of strength and not too small as this will cost a lot of energy.
Don’t look at the distance but at the duration of a climb, 15 kilometres climbing is different to 15 kilometres on flat roads. Try to eat and drink during your climb, because your body needs the energy.