I've used several methods:
- Mash big gear. Saves my lungs so I don't run out of breath. Works until my mighty guads are on fire and I grind to a halt.
- Spin tiny gear. Saves my guads for the town line sprint. Works until my lungs are on fire and I grind to a halt.
- Work out on hills, doing repeats methodically until I get into shape. To my shock and amazement, this actually worked.
Semi-seriously, which is all the seriously I can manage, it depends on the bike and group (if it's a group ride). If it's a fast group close together I avoid standing for climbs -- it can disrupt the flow and even a small wobble or side-to-side rocking can be risky, so I make sure nobody nearby will be affected. I kinda eyeball what the other riders are doing if I don't already know them well. In slower casual groups I leave plenty of room around me so it's okay to stand to pedal. I don't sprint or try to pass people on climbs unless there's plenty of room. Drives me nuts when wannabe racers do that, darting between slower riders on a casual group ride. Nobody is impressed, especially when they gas out near the crest.
One road bike is old school with downtube shifters. Can't shift on the fly while standing to stomp the pedals. Gotta sit, at least for a moment, to shift safely. So I plan ahead whether to sit and spin or stand and mash. Once committed, I stick with it. Although indexed downtube shifters make it easier to shift quickly during that brief moment sitting. With friction shifting it's easy to blow a shift and get stuck grinding a giant gear at 30 rpm and you're pretty much stuck, at least until your legs die and then you panic trying to unclip before you tip over. Fun times.
The other road bike has brifters so I can shift while standing. Makes it smoother and easier to switch between sitting and standing to distribute the effort for longer climbs.
My favorite hybrid has a 30/40/50 triple chainring and 11-32 cassette, and bar-end shifters on an albatross bar. I hardly ever actually need to stand to climb, but I'll do it occasionally to stretch the legs and cool off the taint. Mostly I sit and spin like an eggbeater.
As other folks suggested, check out the GCN videos on climbing. While the presenters are all retired pros they're far from elitist and mostly aim toward the recreational cyclist who wants to get better. Lots of "cheats" that help conserve energy. One particularly good video showed about half a dozen of the presenters, including Emma Pooley who's a mountain goat. Interesting to watch the different styles of each when they all try to finish an entire climb without ever sitting.