I am just trying to stand too and got some great advice from a friend, similar to whats here.

I click up a few gears - 3 or 4! Then I stand but keep my butt over the seat. I also try not to increase my speed which seems to be the key to not expending too much energy - I even click up one more if I need to slow down.

I also try to stand up at a certain point at the hill in our local Park. Each week I try to start standing a bit sooner. It really works too - I did a long ride and was able to stand and slowly climb a one block hill that often makes me tired.

Of course a few blocks later I crashed into a stone wall and had to go home on the subway, but it wasn't while I was standing!