First thing you do is throw the battery on a battery charger. These are simple machines with a red and black alligator clip, and a common electrical cord. They supply 12V-ish power, and have a voltage regulator so they will correctly charge the battery without overcharging.
A typical battery charger worth owning is 5-12 amps in normal mode. (may also have a ~2A slow charge mode and a 20-60A boost mode, but you want normal mode).
More amps never hurts, but it costs money, and you don't really need more. Slam-charging a battery with lots of amps will prematurely age a battery.
A typical battery is 80 amp-hours new, so you can do the math on that, it may take 8-15 hours to fully top up the battery.
Allowing a battery to go stone dead is also bad for the battery and will age it somewhat. Car batteries are very, very bad at deep cycling (being run down dead then fully recharged).
Unfortunately, lots of things reduce their life. Using them, not using them, overcharging, letting them go flat, looking at them cross-eyed... generally if a car battery is older than 5 years, it's on borrowed time. So if an old battery has gone dead, you can try to save it with a slow (~10A) charge, but be prepared to say goodbye.
Is that a terrible battery design? Oh you betcha, but it's cheap, and it's good at one thing: the huge surge of energy needed to start an engine. You can get a 40-year battery that weighs 500 pounds (nickel-iron) or 500 dollars (nickel-cadmium e.g. airplanes), and lithium batteries show some promise but they're expensive too.
Fuel and consumables
For a storage period of months, you really don't have much of a worry. The worst problem you will have if your area has winters, is "winter fuel" vs "summer fuel", which has different boiling points; just put fresh fuel in there when able.
Even out to a year, this won't be a worry.
Once you're out past two years, you have to start worrying about the fuel turning into varnish in the tank and equipment. Ask anybody who started up a lawnmower that's sat for 10 years, you can spend an hour chipping varnish out of the carburetor bowl. And those are super simple carbs.
These days, everything is fuel injection. Varnish will break the fuel pump, plug filters, plug lines somewhat, and mostly, plug fuel injectors which are extremely fine because they make a fine mist of fuel. Fuel injectors can be sent out and cleaned.
Another issue is the 10% ethanol in the fuel breaking down and turning into stuff that is corrosive, which can then rust the tank interior and in particular, the delicate brass electrical connections for the fuel pump and fuel gauge sending unit.
Watch for coolant problems
The other issue with extended storage is coolant. It doesn't evaporate, but rubber hoses can rot or be chewed by animals who are making their home under the car since it never moves. This can cause a leak, either immediately or later when the system pressurizes. As such, once you get the car going again, it's easy to accidentally run the car with no coolant in it. The car won't tell you anything until it overheats, by which point damage is starting to be done. Unfortunately most people do not take overheat warnings seriously, and continue driving "because what else can I do?" This will warp the cylinder head, greatly increasing repair costs... and eventually reduce the engine to slag.
What you do is pull the car over as soon as practicable, let it cool down for 1/2 hour, then try adding water if you have any... and if you are able to refill it and the leak is slow enough, try limping it to a nearby place it can be serviced, again shutting off and letting it cool if the overheat light returns. Sometimes that works, sometimes it doesn't. If that is not viable, then just have it towed. It's cheaper than resurfacing a head.