I've a 77 impala that hasn't been started in several years. What should I do before starting it.
just

Dang that's a popular video type on YouTube now, people find old vehicles that haven't run in a long time and get them started.

If it were mine..... Without any fuel hooked up to the carb (so as not to flood it) and with a fresh battery, crank it over until you've built up oil pressure on a mechanical gauge, and check for spark while you're at it. After you've got oil pressure and spark, hook up the carb to a temporary fuel tank (set up high so it'll gravity-feed) and pump it a bunch, looking for squirting from the accelerator pump. After a squirt of fresh gas down the carb, you should be good to go. If it won't run, you'll probably be looking at a good carb clean out/rebuild, if it's all gunked up.

If you know for a fact that the fuel tank isnt rusted internally, you'll probably be good to just drain it out and fill it with fresh gas. If there's a chance it's full of rust, you'll of course need a new tank (or at least a good filter).

I've brought a lot of cars back from the dead. Some dead ones for 10-20 years.
Check usual stuff , oil , antifreeze, gasoline quality. Belts , hoses , look for leaks.

Having a fire extinguisher close by is a good idea.

After it starts , run it for about a minute , then check everything over again. After running it 5-10 minutes , changing the oil&filter is a good idea.

I’ve got an old jeep I need to fire up soon, I plan on putting a little oil in the cylinders put in fresh gas and I have a beater battery to start with.

Mostly wondering about damaging the cylinders since they are probably dry.

Put the lube of your choice in the cylinders depending on when you plan on turning the key, several ways to do it depending on the engine make up. Doing a fresh oil change might help the top end a bit.

I would put in an aftermarket in-line fuel filter at the carb too.

Dump a bit of oil down each cylinder, turn by hand to make sure motor is loose, turn it over a few times with the plugs out.

I wouldn't worry about it too much if it's not stuck, if you let something sit over winter the cylinders get dry and you start it, just let it idle and don't rev it up and you should be fine.

Put a good splash of ATF in each cylinder, crank it for a while with the plugs out.

Turn it by hand after lubing the cylinders.

My old mechanic buddy would suggest pulling the plugs then squirt some marvels mystery oil down each cylinder and let it sit for a bit then try to turn over the engine by hand with a breaker bar and socket on the flywheel bolt replace the spark plugs .

Let us know how it goes .

I'd be more concerned with the fuel system.
Could run it from a gas can to check that.

Has a 4 door, slept 4 + 2 in the trunk.

If the engine can be turned over a complete revolution without any tight spots, I move on to providing for an alternative to using fuel from the gas tank.
My go to is a plastic boat tank including the primer ball and put the hose on upstream of the fuel pump.
Varnish in old gas will gum up the valve stems and guides and bend push rods. It will also do no favors for your carburetor or the check valves in the fuel pump.

Put oil in plug holes. If its easy to remove valve covers do it and squirt oil in there.
Turn it over by hand.
Put plugs in, turn over with starter, no fuel hooked up.
Get a small tank for fuel to bypass fuel tank. Put plugs in and see if it starts. Dont rev it up for a couple min.