Humidity, Temperature, and Storage
Your guitar is made of thin wood which is easily affected by temperature and humidity. This combination is the most important single part of your guitar's surroundings. I keep my workshop at a constant 45-55 percent humidity and 68 to74 degrees Fahrenheit. If either humidity or temperature get far away from these conditions, your guitar is in danger. A rapid change in temperature or exposure to cold can cause small cracks in the finish. These are lacquer checks. I recommend the use of a hygrometer/thermometer to measure the relative humidity and temperature surrounding your guitar.
As humidity increases, moisture content of wood goes up rapidly, causing it to expand and swell. A gradual increase in humidity won't generally do permanent damage to your instrument. When very high humidity is combined with high temperature, glue joints could possibly become weakened and may even open slightly. If your guitar is exposed to high temperature or humidity for any length of time, the glue under the bridge could weaken causing the bridge to pull off.
Rapid changes in local humidity are what you want to guard against. If, for instance, you place your guitar near a source of dry heat, the humidity around it will drop much faster than it would naturally, although a sudden dry spell can have the same effect. If the moisture content of wood is forced down in a hurry, portions of it shrink faster than others, causing cracks and open joints. Don't set your instrument next to a source of heat or hang it on a wall where it will dry out. At all costs, avoid hanging your guitar on an outside wall during winter months. The wall will be cooler than the inside air. The result is a conflict between the temperature of the top and back, with potential damage as a result.
Should the guitar be exposed to freezing temperatures, let it warm to room temperature while still in its case. This allows it come up to room temperature more slowly, decreasing the possibility of wood and finish cracks.
Caution should be taken if you choose to use a humidifier to combat low humidity. Moisture in direct contact with the guitar could cause damage, as can the rubber or vinyl parts of a humidifier. Using a console model evaporative humidifier for the house is a good idea. I recommend storing your guitar in its case when not in use. Don't bother loosening the strings when putting your guitar away unless it won't be used again for several months. Constantly tightening and loosening strings quickly ruins their sound.
The hard shell case supports the neck and body of your guitar as evenly as possible. It's important that you don't let anything lie under the head (the tuning machine end), as this could damage the neck and body.
Repairs to your instrument should be performed by a skilled repair person.
Cleaning the Finish
The best way to clean your guitar is with a soft cloth. Your guitar is coated in the highest-grade finish available and is sensitive. Any type of solvent, especially those found in plastic, vinyl and leather straps, will mar the finish, as will alcohol, citric acid, aftershave lotion, insect repellent, and a number of related substances. Perspiration can also damage your guitar, so keep it dry. To polish it, use a special guitar polish and a clean polishing cloth. I recommend wiping down your instrument and strings with a soft, dry cloth before storing to remove harmful skin oils. Products containing silicone should not be used.
Changing Strings
When changing the treble strings, singe a ball in the end (away from the guitar) and tie a half-hitch knot as I did. A larger knot is necessary with carbon trebles. The knot must be bigger than the hole in the bridge tie block. This way the strings will not slip thru the bridge holes and whack the top when tuned to pitch.
This article is adapted from the Martin Guitar Co. to be more relevant to your Lester DeVoe Guitar.