Try shifting up into a harder gear before you stand up then down again when you sit down, also when you sit back on the saddle keep pedalling so you don't lose any momentum.

I would disagree with the above comment. I think its a classic mistake and one which I used to do myself. I used to think that because I had a good core that my body could handle the strain of an extra gear higher when out of the saddle, but unless you're spinning 110 rpm while sitting there is no benefit to shifting up while climbing a steady grade. You will just tire more quickly and be slower in the long run. The key is cadence and rhythm. When doing long climbs i.e. ones that take more 3-4 mins, the most efficient way to go fast is to sit and spin between 75-90 rpm (depending on your pedaling form/power maybe higher) and an out of the saddle effort should only be used for short periods (under a minute for me) if the grade kicks up so as to keep the cadence within that range, or to give the sitting muscle groups a rest. As an earlier poster commented, out of the saddle is slower going uphill than seated so to keep the same speed you need to be spinning faster. Shifting up will just fatigue the legs for no gain.

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"Je pédale, donc je suis" - René Descartes (I think )

2011 Canyon Aeroad CF
2012 Canyon Ultimate Al

I'm not talking about standing all the way, but it helps me to stand every now and then, and when standing it's best to shift up to take advantage of the extra power put into the pedals. Spinning up a long climb at exactly the same cadence is fine if that works for you as a means of getting to the top with the least amount of effort, but fast it isn't and it certainly will not improve overall climbing performance. If the OP wants to improve he would need to train on the hill, the old 2 x easy then hard cadence works for me.
Remember a good place to attack is nearing the top of a climb.

Watch how the pro do it. my favourite is out of saddle "Attack" when the group enters the hill. Shift at least 2 cogs- but depends on yr speed n rpm, normally at 90rpm, u can mobe 2 cogs for out of saddle power off. Didn't Andy drop the chain during this classic attack with Mr "C" who eventually won the TDF. I always enjoy attack up slope, that's where my LW shines and please don't tell Me that wheel stiffness is not important.

Attacking out of the saddle is a different question then climbing out of the saddle. gear selection is situational and personal.

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WW Velocipedist Gargantuan