CLEANING:  Keeping your instrument clean is one of the easiest and most important things you can do. Unfortunately the moisture (sweat) that comes from your hands is one of your instrument’s biggest enemies. Yet by just wiping down the guitar after each use, you can all but eliminate any damage that might otherwise occur.
It is a good idea to keep a clean, dry, soft cloth in the case with your instrument. A regular cloth diaper or cotton tee-shirt works great. After you play, take a few moments to wipe off the strings, neck, and body, especially the area around the bridge where the hand rests. By doing this you will greatly increase the life of your strings and prevent the kind of dirt buildup that can harm the finish. Then once a week or so, clean the whole instrument with a warm, damp, soft rag. That little bit of water won’t hurt anything and will clean off all the dirt buildup. Be sure to dry the instrument with your dry cloth.
Using a good quality guitar polish also helps keep your instrument in top shape. There are many fine polishes on the market (I like MARTIN guitar polish), so check with your local music store to see what they recommend. Don’t use furniture polishes which contain harsh compounds like abrasives or silicone. These will do more harm than good in the long run.
For those hard to clean areas, a good idea is to use a soft bristle paint brush, one to two inches wide. Use it to brush away the dust and dirt in all the hard-to-reach places, like under the strings on the headstock, around all the bridge parts (especially on electrics), and around the pick-ups and neck.

STRING CLEANERS AND LUBRICANTS: String cleaners are great! These products help give you that extra life for your strings between string changes. While they won’t make the strings sound like brand new ones, they will maintain a good quality sound until you are ready for new strings.
Some people like the string lubricants that are also available. The idea here is to make the strings and fingerboard slicker so you can move faster up and down the neck. Lubricants may not be for everyone, but give them a try and see if they’re for you.

TEMPERATURE & HUMIDITY: The weather is a factor in determining what condition your stringed instrument is in. For the most part, it’s the humidity, or lack of, that has the biggest effect. When the humidity goes up, (more water in the air) the instrument takes in water, making the wood swell. Generally speaking, high humidity (causing the guitar to be fat with water) doesn’t hurt the instrument but often the instrument doesn’t sound as “bright” or “crisp” as it might under lower humidity conditions. Of course, like anything left in a damp environment (like a basement), your instrument will mildew which is a no- no for your guitar and your nose!

But BEWARE when the humidity goes down.
Usually low humidity conditions exist in your home during the cold winter months because the heater dries out the air. When wood loses its moisture, it shrinks. When wood shrinks, it pulls away from itself, causing cracks to develop. Things like the solid wood panels on acoustic guitars (tops, back, etc.) are very susceptible, as are fingerboards and bridges. Thicker blocks of wood, such as the body of an electric guitar, or laminated woods (plywood), are less prone to cracking.
During the winter months, when you’re not playing, keep your guitar in its case with some type of “humidifier” to keep it from drying out. You can buy guitar humidifiers or you can take things like oranges (cut in half), or a wet sponge and place them in a baggie and put that in your case. Any of these will help keep moisture in the guitar case and thus in the instrument during the dry winter months.

When you take an instrument that has been out in the cold and bring it into a warm environment you must let is warm up gradually in its case. If you don’t, the wood and the finish may warm at different rates causing finish cracks. So always leave your guitar in its case to warm up, after it has been out in the cold!!

Extreme heat on the other hand (like a closed car in summer), can cause the glue to weaken and damage the instrument. Also, always keep your instrument away from heaters and heat ducts!

ABOUT STRAPS: Take note that plastic, vinyl, and synthetic straps can and will damage some types of guitar finishes. Also, straps with buckles, chains, and other metal parts will cause bad scratches if not handled properly. So be aware of your strap and pack it separately from the instrument if it could damage the finish.

GUITAR STAND: A guitar stand is a must for those times on stage or during practice when you don’t put the instrument in the case. If you lean your guitar up against a chair or table or amp, it’s going to fall and you’ll be sorry!!

ABOUT TRAVEL: If at all possible, let your guitar ride in the back seat and not in the trunk. In the summer with the windows up, your car is like an oven. This excess heat can cause the glue to loosen around the neck and bridge and brace areas. This can result in major damage to the instrument.  If the instrument is left in a cold car, remember when you bring it in to let it warm to room temperature in it’s case to avoid finish cracks.
If you’re flying, see if you can carry on your instrument. You may want to call ahead to find out about carryons. If you have to check your guitar through with the luggage make sure it is in a hard shell case!!!  Some think you should always loosen the strings when the guitar goes through luggage, I’m on the fence about this one, but at least fill any air spaces in the case (like around the neck) with some of your soft clothing. This will keep the guitar from rattling around in the case and help to avoid damage. When I fly I prefer to bring my guitar in a good strong gig bag and carry it on. I have had good luck with this as the guitar usually fits in the overhead and is under my watchful eye. As a repairman I see all to many damaged guitars that were checked through with the baggage.

REMEMBER, be careful and be smart when traveling with your delicate instrument.