Procure a clean copy of the service and owner's manual that corresponds with the particular tape recorder that you are restoring. Online auction sites as well as local electronics shops and technicians are good resources for hard-to-find service and owner's manuals.
Remove the outer casing from the tape machine with the appropriate tools. In most cases, all you will need is a screwdriver set and hex wrench. However, some tape recorders are more difficult to disassemble than others and require special methods. Consult your service manual if you do not know how to properly remove the outer casing.
Visually inspect any moving rubber parts that you can see in the machine. If they look slick and worn, they need to be replaced. Consult your service manual for the exact type of part you need to replace. The most common worn areas on vintage tape machines are the capstan, belts and pinch roller. The procedure for rubber part replacement varies from machine to machine, so consult your service manual for detailed instructions on how to replace the parts.
Apply a small amount of switch and contact cleaner to moving metal parts inside and outside of the tape machine with a cotton swab or applicator. This will help to reduce squeaking and keep the parts from wearing out too quickly. Check your manufacturers recommended switch and contact cleaner type for best results.