Here is a simple list of maintenance tips that you should do if you want your crossbow to be always at its best:
String and cables should be waxed
When you purchase a crossbow, you will be most likely get a tube of wax along with the package. If you don’t, you have to buy some. The wax is used to maintain the string and if you are using a compound crossbow, you should also use the wax on the cables. You should consult your instruction manual as to how often you should be waxing your string and cable. To do so, apply the wax to the length of the string or cable, avoiding the part above the arrow rail so that it does not affect the trigger box. After application, rub the wax using your fingers. The heat generated from your fingers will melt the wax and make it stick longer.
The rail should be lubricated
Lubricating the rail will give a smoother traction of your arrow with less friction and more accuracy. To do so, add two drops of lubricant to the center of the rail. Using your finger, sad the lubricant across the entire length of the rail evenly. Make sure that you do not use vaseline-based lubricants on your crossbow.
The exposed mounting bolts and trigger box should be lubricated
In order to avoid the exposed bolts from corroding or getting weather-induced damaged, you have to lubricate the exposed mounting bolts. The trigger box should also be lubricated so that the trigger will work smoothly. Apply two drops of lubricant to the trigger box. For compound crossbows, you also have to lubricate the axles and wheels.