I want to buy [something] from [a DSM vendor]. How can I avoid problems?

[Note: the information discussed below defines a 'DSM vendor' as an established legal business that sells parts or services for DSM cars, and not private individuals selling parts or services.]

You can avoid some common problems by keeping the following in mind:

• Most speciality DSM vendors are extremely busy, and it can be hard to get into contact with them. Be patient.
• Know what you want. Most speciality vendors have web pages that describe their offerings in detail. See the vendors page for the appropriate URLs.
• Know what you have. Be prepared to tell the vendor not only the make and model, but if you have factory options (like air conditioning and ABS) or upgrades (such as Big Brakes, shocks/springs or 4-bolt rear ends) installed on your car.
• Be sure to ask if the part will fit your car before ordering it.
• Ask about warantees and returns. Understand the limitations of the return policies. If you don't like them, don't order the part.
• Write everything down! You may need the details later.
• Pay with a credit card. If you have difficulties later, you can have your bank reverse the charges on the card.
• Ship to your credit card address - the vendors require this so they can avoid credit fraud. If you need to ship to an alternate address, call your credit company ahead of time and establish an alternate shipping address - the vendors cannot do it for you.
• When purchasing parts, establish a shipping time for the part and a shipping method. Do not assume the vendor will automatically ship the way you expect.
• Foreign customers must expect additional delays and costs for customs when parts cross the border. Do not expect the vendor to understand what is involved here - it's not their business. 

Support for DSMs has become very limited to niche areas, even at previously well respected vendors, due to lack of demand. Be prepared for lengthy delays, and discuss availability with the vendor before ordering. Face it, you own an obsolete car.