Ooh, I love this question.
So first up:
You will want a fairly large trampoline in an open space, and you will want it positioned in a place where you can (more or less) shoot against the sky. Unless you want your neighbours’ houses or trees as the background, an open sky is the best because you can fake supreme heights by just removing the few little distractions that squeak in and photoshopping in some clouds or some land below or something.
You will absolutely need a photographer. I don’t think tripods really matter because you’re going to be moving around so much that the freedom of movement is much better for the photographer if they can move swiftly, too.
You want to pick a day that has nice lighting. Overcast is great because you don’t end up with harsh shadows on your face and whatnot, but it can also make pictures a little grey. No problem, you have post-production to fix that. Also pick a day where you’re not going to sweat your ass off; we did our first trampoline shoot in 40ºC weather, and afterwards, I could practically wring the sweat from my skirt where the belt had pressed it against my skin. (Beautiful mental image, I know. I’m just trying to spare you the Gross.)
Any heeled or unsafe shoes for trampolines are a no-no. Jumping around in my sock-boots with thin, flat soles for Supergirl is great, but I’d never jump in heels, both to protect my own ankles and protect the trampoline. Likewise with heavy boots. You don’t want to injure yourself or damage your trampoline (or your friend’s trampoline, or whoever’s) just for cosplay pictures. Is your footwear crucial? Wear coloured socks or make alternate shoes that are “lightweight/flat” editions of your regular shoes. You don’t need heels for height when you’re being flung through the air!
The biggest trick to actually doing these photoshoots is controlling where the cape goes. If you just bounce around and let it go wherever it pleases, you are going to end up with it going over your head, wrapping around your body, getting caught between your legs, etc. You need a cape that is long enough for you to hold onto the edges. Ideally, you are going to hold onto it to guide it as you go up, and let go juuust when you start descent. This way you aren’t holding your cape, but you have it spread out beautifully and your hands are wide and “joyous”.
Stop periodically to review the pictures with your photographer. Figure out what is working, what isn’t, and what you need to try again to see if you can time it better/get luckier. If you need to change how you’re working and start calling out timing or make suggestions, do it: communication will make it easier.
However, I also want to note that not all costumes really “work” with trampoline pictures. Josh and I did a shoot once with me in my DCAU/Danvers “white t-shirt” Supergirl costume, with the short cape and the tight-fitting miniskirt, and we found it just ended up looking awkward. In fact, we didn’t get a single picture out of it. We got better pictures out of casual clothes. Trampolines make for very weird shoots; if you only have a little cape flying around you, one you can’t really control, then it often just ends up going wherever it wants. I’ve seen Ms. Marvels pull it off with the sash as the moving fabric or even without, but short capes just tend to be like “hey, did you want me around your head? Done.” I think the “flight” illusion gets a lot of help from loose skirts and whatnot, too. Basically, the more moving fabric you have, the more “dynamic” the picture’s going to end up being. Flying and rushing fabric shows motion. By all means, put whoever you want up in the air, but the more fabric you have, the easier it is. (Unless you’re in a ball gown. Then I don’t know what to tell you.)
But all that aside, I think the hardest part of the shoot is just how much you have to control for. It’s HARD to really nail the shots because not only do you need the camera to be focused and fast enough to catch you when you’re moving all over the place, but you also need to be in control of so much. Your expression needs to be right, so you have to “act” while you’re bouncing yourself through the air. You have to watch how you position your feet and legs. You have to be aware of what you’re doing with your hands, how you’re positioning your body, where your hair is –– it’s maddening work, and while you’re doing it, you have to wrangle a cape and/or make sure your skirt isn’t flipping up. (I have no idea how many shots have been ruined because of that, so I’m going to throw in “get yourself some cute hot pants” as advice.)
And I really want you to be prepared for an insane payoff-to-shot ratio. With us, we usually get about 5-8 useable pictures for every 200 shots we take. If you’re experienced with photoshoots you probably know that lots of pictures end up scrapped in ANY photoshoot, but given the nature of trampolines, you’re just more likely to run into the “shame you’re making a fucking weird face in this shot” problem. Or “oops your cape flipped over your shoulder.” Or “PAAAANTY SHOOOOOTTTTT.”
Flying shots without trampolines.
It can be done, but I honestly don’t have much advice for it, because I largely find it’s unsuccessful. Here’s the thing: when you’re on a trampoline, you’re going to be “up” again in a second, and the elastic nature of it is going to soften the blow of impact. When you’re not, you’re climbing to the top of whatever fool thing you’re jumping off of, and then trying to land on what is probably a hard, unforgiving surface.
As such, it is extremely, extremely hard to do a convincing flying shot by jumping off ledges or stairs or whatever. You will be 90% focused on balancing yourself and not wiping out your ankles or going to your knees upon landing that you won’t even think about where your cape is going. “Jumping off a ledge” gives you “falling” shots, and they don’t even make good landing shots. Also, the distinct lack of height means it’s very hard to get a clear sky/good background that doesn’t look like you’re “falling down in front of this building” or “about to plunge off these stairs.”
It’s also exhausting.
So instead, focus on the going “up”, and have your photographer shoot from a low angle to get a more dynamic view.
The key to this is long straight jumps. You’re much more likely to get a good shot if you’re going parallel to the ground, instead of towards it. Take a good running step and leap as though you’re a ballerina or a martial artist or something.
This is semi-successful, but I didn’t push it enough:
Bend one knee and bring it forward so you’re not a flying stick, and do it dramatically enough that you look like you have forward momentum. That’s how we got shots like the Supergirl vs Powergirl one. They aren’t necessarily as dynamic as trampoline ones, but I think they are better than the “I’m about to wipe out on this concrete, aren’t I?” falling ones.
And if you’re doing fighting poses, make sure your swinging arm is up and away, so you don’t block your body/face with your own arm.
Landing shots and simple cape movement pictures.
These are a lot easier than they look, though just as trial-and-error to get the right effect. What you basically need to watch out for is speed.
Think about it this way: when you move fast, your cape is going to rush, and then it’s going to hit you as you stop because it wants to keep going. If you’re moving fast, you’re also making timing more difficult for the photographer.
What you really want to do here is keep your movements “short”. Start from a standing position and then move forward as if you’re doing an aerobics “lunge” move, dropping down to one knee. Hold the edges of your cape as you start forward and release at the mid-way point. You ideally want your photographer to snap the picture just before your knee hits the ground, when your forward leg is at the knee at about a 90º angle. If you can do this motion slow and smooth, your cape will “glide” with you and your photographer has a better chance at grabbing the picture at the right time, in focus and all that jazz.
Want to just get a “standing” shot where your cape is in motion? Instead of turning in full circles (which gets you shots like this) or running to get your cape moving, try a quarter-turn. That’s how Elemental and I got the awesome shot in front of the grey brick wall. Start with your left side to the photographer, holding the right side of your cape with your right hand. When your photographer is ready, swing your right leg to turn yourself to face the photographer and let the cape fan out. The quarter-turn gets just enough motion running through your cape (and skirt) that you get movement going on without going so far that a) the photographer loses you or b) your skirt flips up. The quarter-turn also means you can be facing your photographer the whole time, instead of trying to look at them while spinning in circles.
Hope that helps :)