Whatever type of riding you do, you can be a better climber by tweaking your technique and following a few simple rules - no training required!
Fix your style
Your riding style will depend on the type of hill you are climbing. On longer drags you will be sitting down. The best way to climb these hills is to grab hold of the centre of the bars and pull with your arms, while sitting back on the saddle and concentrating on your pedalling. A steady rhythm is critical for this type of climbing and you must bring your ankles into this technique.
On these climbs, use your feet and ankles like this: concentrate on your feet in small gears on the hill, make sure you drop your heel, but only slightly over the top of dead centre (don't exaggerate the movement); then 'claw' the pedal round at the bottom of the stroke and pull up with your heel slightly raised, while dropping the other heel slightly and pushing down.
There is no need to overly concentrate on the pulling up of the foot, because this should happen naturally on a climb. But keep some upward pressure while pushing with the alternate foot. Try to think 'smooth' - the best way to imagine it is performing a small circular movement of the feet.
You should keep concentrating while practising this and make sure it's a smooth action all the time; nice and fluid. At the same time stay relaxed on the bike, but keep that upper body still, with no rocking of the shoulders, and think 'power'! This is where work in the gym on the upper body really comes into its own and is a very important part of my athletes' work.
Upper body strength: gym'll fix it
You can't climb efficiently with poor upper body strength, so get down to that gym.
On steep climbs, you will be out of the saddle for at least some of the time and again, you will need a strong upper body to control the bike while doing this. As before, use your ankles and pull up even more on the upstroke of the pedal, keeping it smooth. This type of climbing is normally called 'honking', where you are usually on the top of the brake levers and moving the bike from side to side.
Keep it straight
You must concentrate on keeping the bike moving in a straight line, and don't weave all over the road. If you have to weave, you are over-geared and not climbing efficiently. Get that gear down and keep the bike moving in a straight line.
Choose your position
If the road is wet you may get rear-wheel 'slip', so move your centre of gravity forward or rearward to keep that forward motion going and the rear wheel from slipping. You can lose so much momentum if the rear wheel slips, so make sure you understand how to move your centre of gravity over the rear wheel to stop this happening... practise!
Don't go backwards
When you're climbing a steep hill in a group and you have to get out of the saddle, please be aware that someone may be on your wheel - so don't commit the cardinal sin of pulling the bike backwards by about two feet as you raise up off the saddle. Ease yourself smoothly out of the saddle and don't move the bike backwards at all. I've seen so many crashes caused by riders doing this, so be aware of riders behind you!
Do all of the above and you will become a better climber. And remember the watchword is, as usual... practise.