Now that I've been on safari and survived, I figured I would compile the things that worked (and warn against what didn't) and share them with the world. Not that I know everything, by a long-shot, but when I do go on safari again, there are a lot of lessons learned that I'd take advantage of.
Pack lighter. I thought I'd gone pretty light, but I realize now that I didn't really need the fleece, or the spare pair of yoga pants. Or snacks for an army. Or 12 rolls of travel-sized toilet paper.
Bring a few different camera batteries, a charger and a memory cards. You know, just in case. I always wanted two back-up batteries for each camera. I took a slew of photos a day (3700 shots over 12 days) and never wanted to miss one because I was low on power. Same with the memory cards. I also split photos up into logical segments by card. Tarangire on one, Manyara and Ngorongoro on another, Serengeti on another. I also found a battery charger would charge my camera battery faster than leaving it in the camera (and freed me up to use my camera while the battery was charging).
Take the best camera you can afford. The best thing I did was buy a new camera about 8 months before the trip, and learned how to use it well. You won't regret it, I promise.
Don't bother with "insect repellant" clothing. Seriously, the one day that I wore the insect repellant pants, my legs got eaten alive in Manyara. You STILL need insect repellant spray or lotion. Believe me. Paying extra for these pants was not worth it.
Go with sports bras. No matter how well-endowed you are, or not, sports bras provided better....coverage, shall we say, on the very bumpy roads of Tanzania. The one day I wore a regular bra, I was pulling the straps up all day, as they kept coming loose and falling down. I wore sports bras the rest of the time.
Shower before dinner. We learned quickly that we'd be sweaty and dirty from just about the moment we set out in the morning. By riding in an open topped, open windowed vehicle on dirt roads all day in the beating sun, you just don't have any other options but to be dirty. If we showered right before dinner (when the game drives of the day were done), we would be cleanest longest, clean for sleep, and ready to spring into action first thing in the very early mornings with minimal prep time.
Reconcile yourself to not looking gorgeous. You're on safari in the bush. With the top up and windows down, the wind's going to be blowing as long as you're moving. To think your hair can keep up is silly. To think that make-up is not going to get covered up with sweat and dust is sillier. Just don't bother. The animals don't notice anyway, and they don't know how dolled up you usually are at home!
Take binoculars enough for everyone. Sure the vehicle will have a pair or two, but I found that on the important sightings where we'd wait for a while for some action, it was difficult to want to (or have to) share. Everyone should really have their own pair, I think.
Don't bother with guidebooks. I would say that if you're only going on safari and not doing any independent city travel, you don't need a guidebook at all. Your guide will more than cover whatever you're seeing in the parks and conservation areas....however.....
Take a wildlife guide. I took Wildlife of East Africa and loved it. It is just big enough to contain great color photos and succinct descriptions. It is well-organized and thorough (there was nothing we saw that wasn't in the book). Our guide had a book too, but this was a nice supplement.
Keep a wildlife log. I took a very small notebook and a pen out with me on each game ride. I started a new page for each day and wrote where we were, the date and then listed every wildlife sighting in order. This made it easy to figure out "what that is" when I was looking at my photos when I got home.
Take TP, hand santizer, baby wipes. I'm normally a hypochondriac traveler, always afraid of catching something, but more so in Tanzania, all of this stuff came in really handy. Travel-sized rolls of toilet paper (which come in handy plastic cases) were helpful not only when we'd stop to go in the bush, but also in the few permanent facilities we came across that weren't stocked up. The hand santizer is a no-brainer, before and after bush toilet breaks, before eating, etc. The baby wipes were surprisingly useful, especially to freshen up a bit during mid-day siestas when it was too early to shower but we were already feeling grimey.
Bring a travel mug. If you love coffee, you will absolutely adore Tanzanian coffee. Every morning we left early for a game ride, I wished I'd had a travel mug to take it out on the road with me. This is one thing I MUST do next time!
Take a day bag. This may or may not be your carry-on on the plane, but this was the bag that went out with me every day. Its contents: cameras, batteries, memory cards, wallet, hand sanitizer, TP, wildlife guide and notebook log, binoculars, bug spray, sunscreen, sunglasses, hat, light rain jacket, anti-diarrheal, allergy and other medications, snacks, lip balm (SPF 30), kleenex, iPod.
Music. On some of the longer drives, I'd put my iPod on and listen to a soundtrack I'd prepared at home. Now when I listen to that same playlist, I get carried back to that drive and that scenery in my mind.
I hope this helps others getting ready to go.