Hey @joannapotter !
I assume this is your first portrait shoot (so congrats!). I think you’ll have a lot of fun.
A huge part of getting good portraits is good lighting. If you’re doing this outdoors, you’ve got two options: shoot within an hour of sunset or sunrise (golden hour!) or shoot whenever you’d like when it is overcast. If you’re going the golden hour route, I really like backlighting my subjects by having them face away from the sun. It’s a good way to get an airy look to your pics and it can look quite good. If you’re shooting when it is overcast, there will be less light, but it will fall evenly on your subject without harsh shadows. If it’s bright and sunny outside and it’s during the middle of the day, either reschedule your shoot or find some even shade.
Camera settings depend on what you’re going for. When I’m shooting portraits, I like to use a wide aperture (think f/2.8 or however wide open your lens will allow) and a fast shutter speed to avoid any motion blur. If you’re shooting headshots, focal lengths around 85mm look very nice (so bring your telephoto lens if you’ve got one!). I think the last time I shot senior portraits, I was using my 50mm f/1.8 a whole bunch, which would be another good choice, especially for head-and-shoulders or half-body shots. Don’t be afraid to change it up and try different lenses for different poses!
I find posing to be one of the hardest things to do, and usually I find that looking at other photographer’s work can give me ideas. I know Lenspiration does have a posing database if you have a paid account (https://www.lenspiration.com/proposing/). Looking up “senior portraits” on the Internet would probably yield some results that would not be Lenspiration-appropriate… but I’ve found that looking up things like “family photo posing” or “how to photograph your kids” tends to yield better results (I really like clickitupanotch.com but it’s more geared towards photographing small kids). You really want your subject to look as natural as possible. Giving her something to sit on or to lean against can go a long way! Try a lot of different poses and shots and get creative. Maybe try to incorporate her interests and activities too.
Have a few jokes ready or do something else (or have her do or say something odd) to make her laugh… you can get some really genuine smiles this way.
Editing goes a long way in giving photos that extra pop.
Good luck to you!
—Logan