Before I do a portrait session, be it on location or in studio (read studio as living room), I have a process of checking, double-checking, then thrice-checking my gear and shot lists to ensure no soldier is left behind. The things I go through may not be for everyone, but hell, it's my process.

Before Shoot-day
- Ensure you have a client / model to shoot. Ok, given - but it really makes the portrait session turn out much better.
- Night before, charge all batteries (or be sure you have spares if you don't use rechargeables for some reason). These are the batteries I check:
- Main body (and if you have a spare, be sure it's charged)
- Battery grip
- Triggers (one on camera, one backup)
- Trigger-receivers (4 + 2 backups)
- Speedlights (4 plus one backup)
- Back-up CF cards formatted (usually bring 4 spares)
- Ensure L-grip for my tripod is mounted to body (imagine showing up with a tripod, and no way to connect to it?)
- Figure out my shoot-list (research my pool of shots from fotogs I admire)
- Grab hit-list of lenses (35, 50, 100 for me) and be sure glass and filters are dust-free - ensure mounts are clean
- Double-check weather / tides / wind for your location
- Print out model release form
- Confirm once again with client / model about date / time / location - remember, model time does not equate to your watch
Camera Checklist
- Inspect sensor / lens mount
- CF card formatted
- ISO set to 200
- White balance set to appropriate
- Image quality RAW
- Shutter mode to single shot (spray and pray is for the weak!)
- Mode set to manual (not that it has ever left that mode)
- Batteries in body / grip
- Goto lens (Zeiss 100mm) attached and wide open (I love to start wide open, then dial in)
- Set exposure comp to "0"
Shoot-day Pack List
- Camera
- Tripod
- Triggers / remotes
- Cable-release
- Spare CF Cards
- Batteries plus spare batteries*
- Speedlights
- Umbrella stands with brackets / shoes installed
- Umbrellas (4 plus spare) / Beauty dish with sock
- Sandbags for stands
- White / silver / gold reflector
- Lens cleaning cloth
- Sensor swabs - Type 2 (Yes, I have had crap get on the sensor during a shoot)
- Eclipse solution
- Model release form(s)
- Models cell # (she WILL be late)
- Snack - for waiting for the model to show up
- GPS directions plugged into iPhone
- Business cards (someone walking by will usually ask for one)
- Hat / sunblock if in the hot sun
- Change of shoes / socks / pants etc - you never know, you may need to wade knee deep in a swamp to get the shot
*I only use fresh batteries at each shoot.
That's about it for me. It seems like a lot, but basically, it's all second nature now. Better to be over than under-prepared. Feel free to share with us steps that you use!