If you are at ground level, you can land on the ground or objects by commanding your character to sit; movement of any kind will put you back into flight. If you are unable to land on an object, you can shift to caster form; stand on the object; and then, without moving, shift back to Flight Form and order your character to sit.
You cannot use abilities in this form. You are also considered a Beast, so spells that target Beasts can be used on you ([Hibernate], for instance, though you are immune to this while in the air, as flying apparently makes you immune to Crowd Control).
Unlike other animal forms, the Druid cannot drink, eat or use items while in Flight Form.
Flight Form has three specific advantages over a Flying Mount.
Flight Form is an instant-cast spell, making it useful for getting out of sticky situations. While it can only be cast out of combat, coupled with the Night Elves' [Shadowmeld], Druids are able to escape almost any encounter.
Although you cannot use items such as healing and mana potions while in Flight Form, you can interact with the world in ways that a flying mount doesn't allow: you can loot, pick herbs, and skin (but not mine) in Flight Form. This means you are able to avoid danger by increasing your altitude if caught unaware.
Being an insta-cast spell, a player can use it while plummeting, thus saving their life.
Originally, in the beta, Flight Form could be cast in combat, allowing the Druid to escape a potentially messy battle.
Tips and tactics
This form is instant cast, so it can be used to beat a strategic retreat if a fight is going badly. As soon as you are out of combat, it is possible to attempt an instant upwards escape.
Skydiving! With practice and if you are high enough in the air when you start, you can dismount or unshift, cast an instant spell, and then shift back before hitting the ground and dying. In a case where you are being chased aerially, this allows you to heal and re-buff without making yourself vulnerable by landing. Be very careful of crashing when you do this!
Flight Form can of course be used to avoid taking falling damage, by shifting before hitting the ground.
Flight Form can be used to scout or bypass small obstacles quickly without the inconvenience of taking the time to mount up.
This form can be used to quickly bypass content in a manner similar to that of stealth, but with differing limitations. It is also very useful for browsing for herbs, minerals, or rare-spawn mobs.
If there is something you want to loot (herb, skinnable corpse) but there are some (up to three) nearby ground mobs that you don't want to fight, go to a safe distance and cast [Nature's Grasp] on yourself. Shift back to Flight Form and fly to your target area. Go to zero altitude, aggro the mobs and make sure they get rooted some distance away from the object you want to loot. Once they are rooted, you can stay in Flight Form (stay at zero altitude or you will break combat and reset the mobs) and loot the object at your leisure, after which you can just fly up and away.
As of Patch 2.3, your corpse will no longer stay in the air if you die in flight. Your corpse will fall to the ground at the point you died in the air.
In order to do a loop, enter the command /mountspecial. This only works while on the ground and not moving. There are two actions, Pitch Up and Pitch Down, that can be key-mapped to permit gradual loops in motion.
Moonbomb: In a heavily farmed area you can gain an advantage by scouting for mobs and Moonfiring immediately after reverting to caster form and before landing.
RAWRbomb! Shift out of Flight Form while airborne, shift to Bear Form, and Feral Charge your target before you land. Practice until you can accurately land on top of your victims. Important note: You must have the restoration talent [Furor] to get enough rage while falling to be able to [Feral Charge]; if not, you perform a RAWRsplat (unless you time Enrage perfectly).
Sneaky Sneaky Sir: You can even shift out of Flight Form, pop into Cat Form, then Prowl all before hitting the ground. Perfect for surprise attacks! This also allows you to shift out from a higher altitude, with the Cat Form's inherent lowering of fall damage.
Flight Kite: In your Flight Form, at zero altitude, you are able to aggro ground mobs. You can instantly break combat by gaining altitude. And, since you move at the speed of a ground mount, you can easily kite by getting close, getting aggro, and fly away; when you've gotten it far enough, lift off and back they go. Let them hit you once in a while for the damage from [Thorns] to keep them interested. This mechanic can be used to distract mobs around a resource node or quest object that another player can then loot safely. While this is also possible with a normal flying mount, Flight Form has no chance to be dismounted by getting hit from behind.
While the Flight Form doesn't run along the ground, it does seem to act as a ground mount at zero altitude. If you fly down and touch the ground, you bounce up to standard flying beast height, and follow the terrain more slowly than when flying. This seems to allow movement-affecting effects to apply. It's also possible to fall off of things in Flight Form while doing this. You do take falling damage after sliding down steep slopes, unless you have a moment of free-fall, prompting your character to fly again.
Water to Flight Form: rapidly and in this order - jump straight up from the surface of the water, move forward (or backward), then shift into Flight Form.
Cliff escape: if you're caught in a tight spot near one of the endless Outland cliffs and don't have the time, health, or space to run far enough to drop combat, just jump off the cliff. You may have enough distance falling to break combat with the mob, and by spamming flight form you will stop yourself before you die. Note that this is far from guaranteed; vertical distance does not break combat like ground-level distance does.
Farming/grinding quests: when doing quests where you have to pick up 10 items of some kind from the ground, you can fly over the item and loot it without changing out of Flight Form. If all mobs in the area only can do melee damage, you will be able to do this quest with no fighting in less than a minute.
Entering the command /sit while hovering over a flat surface will cause you to perch upon it. Entering the command /sleep while hovering causes you to freeze in place.
Escape Combat: Night Elf druids can use [Shadowmeld] to leave combat and then shift to Flight Form, allowing them to get out of the area. Flight Form of course breaks shadowmeld.
Only the most skilled and powerful of druids are able to learn the mysteries of flight.
Patches and hotfixes
Patch 9.0.1(2020-10-13): Re-added as a passive ability.