Smartphones have become fairly mainstream recently and all I hear is how WiFi kills your battery and how 3G is slow (in most city areas). While both statements above are true, you can get the best of both worlds.
WiFi is often disregarded by mobile users unless they are at home and have a charger nearby. The sole reason being, it can drain your tiny smartphone battery quickly if not used correctly. Although this is a downside, WiFi is far more efficient than 3G when it comes to downloading and extended mobile browsing. Another thing that most people don't realize is that 3G draws more juice than WiFi when actually being used, communicating with the tower is no small task for your handheld device. In city areas it's even worse, everyone connecting makes the network slow which in turn lengthens the amount of time your phone needs to hold a solid connection with it.
Enough with the technical stuff, you obviously just want a fix.
The answer is fairly simple, to get the best out of your phone turn WiFi on when updating applications and watching YouTube videos. (This also will save you precious MB's with the new Data caps! :))
As soon as you are finished with your data hungry task, flip it off and carry on with your day! Leaving WiFi on keeps your phone searching for a network as you roam about during the day. The scanning and analyzing of local WiFi networks is what chews up your battery like a rottweiler. To make it simple for you lazy people who didn't want to read or are not sure when to switch it up, I made an easy to use chart :D Click to view it big! (Note: I am no artist)
At a glance you can tell when to use WiFi and when to use 3G!
Helpful Tip - If you have an Android phone make a widget (like the one below) on one of your homescreens so you can flip it on and off quickly and easily.