Ah, flying. Perhaps the greatest joy of being a witch. The first time I flew was a truly exhilerating experience. Lawks, I even like misflights (though not too often). It provides an adventure, at least.
You'll first need a broom. I know of one location where they can be found--in a secret room in the Gingerbread Cottage. If you're a wette henne, you'll probably be able to convince one of the hags to fetch you a spare broom when you're ready to learn flying. Proper flying brooms are talismans and will tell you to type "broomstick" to see what you can do with it.
Flying uses your broom skills and your direction skills. It is harder to fly at night, and you should always have a light source on your person when flying at night, though that won't prevent misflights. You should bond your broom to yourself so that if it's lost, you might be able to recover it.
It also takes serious GPs to fuel the broom; 200 GPs per flight. You can hold enough fuel for three flights at any given time, but you should always refuel as as soon as possible after a flight--because you never know when you'll need to fly off again in a hurry. The amount of GPs you can fuel your broom with changes as you advance certain skills; you'll figure out quick enough how much you can do at one time, and you can experiment sporadically to see when you up the number to the next easiest round number. You don't want to overfuel; it's a waste of GPs. But you -never- want to underfuel, either, since the result can be a You-Sized crater in the ground and a broken leg that makes it rather tricky to walk. Aulder hags often carry about a portal (made by a wizard) directly to the doctors in case they (or someone they want to help) happens to forget.
Fly-tos are NPCs with names that you can fly to, assuming they are alive when you attempt it. You can also record a certain number of rooms on your broom (which I believe increases based on one or several skills, once you've bonded the broom to yourself), although this does not seem to work well in Terrain. You can fly to other players, too, provided they are outdoors and stay still, allowing us to operate delivery services remarkably well.
Flying is an outdoor sport. You can't fly to or from indoor locations, or people/NPCs who are indoors. Flying from certain situations is also often a good idea; If I get too low on HPs and can't escape any other way, I will fly to a safe spot on my broom (Granny's cottage is #1 on my broom, and always a good place to land).
You will want to bond your broom to yourself (or have an aulder witch do it for you) right away, because this will make it easier to get the broom back, and give you extra slots on your broom based on your ot.dir level.
If'n you like having pets, remember that while Fruitbats will happily follow you into the air, cats and other creatures must be carried when flying, or will be left behind. I've always got my cat with me, and I've taken to carrying her just about everywhere since I never know when I'm going to liftoff. However, I'm a pretty weak witch, so that five pounds is sometimes a pain (though thanks to Flyta's attentions, not as much anymore). If you do inadvertantly lose a pet, remember that the next time you log in (provided they don't get killed or something awful) they'll appear where your license is. Fruitbats can, I believe, be flown to by name, and get called with their whistles, so it's a totally other situation with them.