Things I could not do without:
Equipment: A good mount. A cooled camera. OAG. Auto-focuser. And scope(s) that match well to camera, seeing, and won't overtax the mount.
Preparation: I use Telescopius and/or Bracken's astrophotography atlas and targets to select targets. I then use SGP's framing and mosaic sequence to create the sequences. I always know at what point to start imaging a particular target and when to stop for the night and switch. I try to have at least one alternate in case of localized clouds.
I create dark libraries at home in advance, using a fridge.
Quick Polar Alignment. I use Sharpcap Pro.
Software. I use SGP (I understand NINA and Voyager are good alternatives, and APT is close). I want something that can do autofocus, meridian flips, equipment profiles, framing and mosaics, plate-solving with rotation support, and dithering. I also use CDC (Cartes Du Ciel) as a planetarium program.
Guiding. I use OAG, and encourage everybody to switch if they can afford to, but if you can't, at least guide. Software is PhD2. I loosen guiding parameters when seeing is bad and tighten them when good. I *always* dither, every two frames (I take over 100) for broadband and every frame for narrowband.
Focus. I use a Bahtinov mask initially, and then autofocus the rest of the night at least every half hour. Focusing is only next to guiding in importance.
Flats panel. I use Spike-A-Flat, expensive but nice, however any panel is better than none. I take flats every time, either before or after the session. Between 1/3rd and 2/3rds of histogram exposure.
I've been doing this a while, and it's amazing how many glitches still creep up. It's important to always have spares for everything: Spare usb cables, spare hubs, spare laptop if you can afford it, spare camera, extra batteries, extra flashlights, extra power supplies and cables, small toolkit. When all else fails, power off, reconnect everything, and reboot. Many times a loose usb or power connection can cause head-scratching catastrophes that are easily fixed by unseating and firmly re-seating everything.
Carry extra warm clothes. It always feels *MUCH* colder when you are sitting at the mount. Warm hat that covers ears, warm boots (and toe-warmers!) are essential. I use half-gloves (they reach halfway to elbow but leave finger tips bare) and over-gloves. Several layers of socks, long johns, and upper body wear with a long, warm windproof exterior. Be prepared for the weather to be 20 degrees colder than the forecast. It'll feel that way.
Start well before dark. Give the scope time to acclimate itself, and yourself time to setup, level, balance and connect everything. Always put on CW's before the scope! And use a dew heater if there's a possibility of dew.
Don't drink alcohol (I'm not a teetotaler in the least, but you need all your wits when doing AP and working in low-light conditions). Do keep warm beverages at hand, and plenty of munchies.
If using Windows, make sure it updates between 8AM and 5PM if you can't/won't disable them.
Never update software just before an imaging session. Try it at home first.
I'm sure I've forgotten some...