Whether it's in your car, RV, boat, or part of your off grid power system, batteries are important and need regular maintenance. To do this, you need a few things. First off is a battery brush. These make the job of cleaning the crud that accumulates on the terminals and posts quick and easy. To do this, disconnect the terminals, negative first, using the proper tool for the fasteners. Be extremely careful not to touch metal with the tool, especially on the positive side. Also avoid shorting the battery across the posts, or you'll get a crash course in arc welding! Push the brush onto a post, and turn it clockwise. Just a few twists will do it, and when finished, the post will be bright and clean. Use the male brush to clean the terminal lugs.
To prevent that crud from building up in the first place, get some terminal protectors. Don't know how they work, but they do! It's PFM for all you former military folks.... Also, spray those terminals with protectant for even better crud prevention.
Always keep the top of the battery clean. Moisture, crud, dirt, they can all conduct current and cause your battery to slowly discharge. Never leave a battery in direct contact with the ground for the same reason. Place it on a board, rubber mat, or some other dry, insulating material. In a vehicle, make sure the battery is properly secured in it's tray. For boats, RVs, or other purposes, it's a good idea to keep the battery in a marine battery box, which will prevent objects from falling on the terminals and shorting the battery, possibly causing an explosion or fire.
Make sure the battery box is well ventilated. Charging batteries give off hydrogen gas, which is extremely explosive. Always charge batteries in a well ventilated area!
The last thing maintenance wise is keeping the electrolite level topped off. Lots of batteries today are "maintenance free", but if there are removable caps on top, they are not. Use distilled water only when topping off the cells on a lead acid battery. Tap water will cause scale to build up on the lead plates, reducing battery life. And remember, it might go in as water, but it comes out as acid! It will burn you, and eat clothing, paint, and other stuff. Be careful!
For long term storage, it's best to keep the battery on a trickle charger. Never dishcarge a battery below 50%, as this will reduce it's life. Use deep cycle batteries for power systems, and cranking batteries for starting engines. Choose battery size by the amperage required from the intended load. And there ya have it, battery 101!