Riding out of the saddle is a necessary skill for sprinting
and sprinting is not just used for winning races
you also use it when you're accelerating out of corners
or going after breakaway groups.
Riding out of the saddle is also handy when you're on really steep gradients
and also on long climbs, just to give you're body some respite
from being in the same position
Your position on the bike is also important. If you've got your handlebars too low or your reach is too short
then you'll not only be uncomfortable but you'll also risk hitting your knees on the handlebars as you lurch forward
Another one is the saddle. If that's too far forward, then as you get out of the saddle you risk snagging it on your shorts.
Your cadence when you're out of the saddle will generally be lower than when you're sat down
so before you stand up, just click down a couple of gears in preparation.
Generally riders are most comfortable on the hoods when climbing
so just place your hands there.
Push your body upwards and forwards as your preferred leg reaches the 12 o'clock position on the cranks
This should leave you in the prime position to push downwards when you're up and out of the saddle.
Rock your bike gently from side to side,
pushing it to the left when your right leg is pushing down and over to the right when your left leg is leading.
This will basically put your weight over the top of the pedal that's pushing down, using gravity to your advantage.
Some riders rock the bike more than others,
think Tommy Voeckler versus Bradley Wiggins on the climbs
or Alessandro Petacchi versus Romain Feillu on the sprints
Just like when you're riding in the saddle, your legs should never quite be fully extended,
just leave a slight bend in your knee, even at the bottom of the stroke.
Your body weight should be positioned predominately over the bottom bracket and pedals,
if you've got it too far forward or back, you negate some of the benefits of riding out of the saddle.
Bear in mind that it is very easy to go into the red or over your limit
when you're riding out of the saddle, because you're also recruiting the muscles in your upper body.
If you're on a particuarly steep, wet, or slippery climb
try to keep your pedal stroke as smooth as possible.
If you're choppy, then that could lead to rear-wheel slip.
Finally, as you're getting back into the saddle, just click up a couple of gears again
so you're back to your normal cadence.