Cycling event organizers like to throw at least one "killer" of a climb in their routes somewhere. It's what attracts people to rides: the challenge, the pain, the bragging rights in the bar afterwards, the sense of satisfaction when you survive it unscathed.
Often these are long steady climbs that seem to stretch on for eternity. In this case all the usual principles of good climbing technique apply. Pacing, keep cadence as high as you can, sit up and stay relaxed, alternate between sitting and standing etc...you've heard this before I'm sure.
But, sometimes that monster of a climb is just one little climb which, although short in distance, has a grade percentage on it which is so high it strikes fear into the heart of all those who attempt to climb it. In this case it takes some slightly different techniques to conquer it, where some of the usual climbing recommendations have to be cast aside.
Here's how I approach such a monster:
Go Easy Into the Climb
Sometimes they're right at the end of an event so inevitably you will be tired. But, ease off a little on the run into it, take on some nutrition (an energy gel about 15 minutes before is always a good idea) and try to give your legs a little time to recover.
Don't Attack it at the Base
A common mistake is to just "go for it" right at the start. More often than not this results in legs giving out part way up. I have found the best approach is to go really easy at the base, creep if you have to, be economical with the energy you have, put in just enough power to keep the bike moving forward and ignore others that are sprinting past you. For most people the aim is to get to the top without having to stop and walk, not to race up it and be the fastest. If you feel like you've saved too much as you near the top you can always finish strong and enjoy the feeling of flying past others towards the summit.
To get up a really steep climb you have to be able to stand up as well as pedal when seated. When standing you have the advantage of being able to use your own weight to push down on the pedals as well as your muscular strength. Counterbalance each downward pedal movement with your hands on the hoods and use your upper body to pull against the force of your legs pushing down.
Use Your Core
You are putting in a huge effort with your legs, and at the same time you're using upper body strength to alternately pull on the hoods/handlebars. What connects the two movements is your core muscles. So, if you are flexing all over the place you are going to miss out on a lot of transfer of power. Imagine if someone tried to swap out your nice stiff bike with one that was all loose and flexible. You wouldn't stand for it, and yet having a weak core can be just as bad. So, lock your core, feel your abs working and make your pedaling as efficient as possible.