I could mention half a dozen reasons why you should take care of your guitar but I will only mention two. First, your guitar can last a lifetime and remain in excellent condition if you give it some routine maintenance now and then, and, it's value will only increase over time as long as it is in good condition. Second, and more important, if you give your guitar some TLC on a regular basis it will feel better in your hands, and will certainly sound better as well.
Regardless of how often you play, you should always store your guitar in a place that is not subject to drastic fluctuations in temperature and/or humidity. Guitars are made from wood and as you know - wood breathes, expands, contracts, and warps under various conditions. If you need to bring your guitar from a cold environment (e.g. a cold winter's night) into a warm room, allow the guitar to reach room temperature before you play it. I learned it the hard way years ago when the neck of my beloved guitar cracked (It was a popular model of a brand name guitar and it cost me $500 - a lot of money back in 1968). It had been left outside in the trunk of a car - IN A FLEECE-LINED, HARD-SHELL CASE! - for little more than an hour during one very cold evening in Toronto. I was late arriving and I thoughtlessly grabbed it out of the case and began playing hard in the very first song of the first set. Suddenly..."cwuchangkahajiiing"... the neck bowed slightly, then cracked. Every string went out of tune of course and I had to leave the stage to call and borrow a friend's as a replacement for that night (we didn't have "Guitar Techs" on hand in those days). I had it repaired at a reputable music shop, but it never felt or sounded the same after that. It's long gone and sadly missed. So, the moral of the story is obvious: Be mindful of the conditions to which you subject your guitar if you want to be spared expense, frustration, and embarrassment.
Changing the strings on your guitar is probably the most beneficial chore you can perform when you need some motivation to play after laying off for a while, but it can also inspire you, and make playing more enjoyable, even if you play every day. New strings have a brighter tone, they're clean and fresh, and will most PROBABLY give you better intonation all the way up and down the fretboard. I emphasize "PROBABLY" because intonation depends on neck and bridge alignment, along with well-fingered notes. I'll talk about adjusting the neck and the bridge for best intonation below. Let's first talk about the strings to choose and how to care for them until you replace them with new strings.
As strings are used they get dirtier and become unevenly stretched throughout their length. They also slowly become worn due to the friction between them and the frets when you play. On electric guitars, they also become slightly magnetized, which causes their "output" to be reduced (they're not as loud as they were when new).
Years ago guitarists would remove their strings and boil them for an hour or so because they thought it would rejuvenate them (the strings, not the guitarists). I tried it once and although it did clean the strings, it didn't seem to improve their tonal quality or restore their elasticity. In fact, you have to be carefully to let them cool sufficiently because they'll break very easily if you don't. Beside, once your strings get to the point where the coating is worn away, no amount of boiling or cleaning will improve their condition. However, there is some routine maintenance you can perform to make them last longer and keep their tone.
Keep a small rag handy and wipe each of the strings lightly after every use. Doing so will remove the oils and dirt your hands exude (regardless of how clean your hands are). In addition to the rag you should keep a few strips of those colorful scouring pads in your guitar case. They are not as abrasive as steel wool (which you should NEVER use!!!) You can buy them at most grocery stores, supermarkets, or hardware stores, and they usually come in a pack of half a dozen rectangular pads about 3 inches by 4 inches and are about 1/16 inch thick. Figure GM-1 shows an orange scouring pad. Cut one into 1-inch by 1-inch strips and use them to wipe your strings once a week. One pad will last a lifetime. I lightly run the piece along the length of each string 3 or 4 times to remove any dirt and oil. CAUTION! BE GENTLE AND DO NOT WIPE ONE STRING MORE THAN A FEW TIMES OR IT WILL HEAT TO THE POINT OF BREAKING!
Wipe the fretboard, neck, and body with a dry cloth, or, if your feeling ambitious, you should loosen the strings and really give the fretboard a good cleaning with a mild wood cleaner every 3 or 4 months, at least. Don't use strong detergents as they can damage the wood. Remember to always wipe your strings afterward, to remove any splashed cleaner.