Does the person behind the parts counter at your local dealership smile when you walk through the door, or do they always seem to be mysteriously disappearing into the back room as you approach the counter?
The best way to be greeted with a smile is to know exactly what part you need before you go to the dealership. Right down to the part number. The best way to know the exact part number is to have your own parts book for the machine under repair. Some parts books for simple machines are $30 to $50. A multi-volume parts book for a late-model combine or tractor could cost more than $500. But it can save lot of time and frustration to look up a part number and call a dealership to see if they have the part before making the drive.
A "free" alternative to buying printed parts books is to look up parts on the internet. Most manufacturers have on their website some way for customers to access some sort of parts breakdown for many of the machines they support. I often use web-based parts "books" when working on shortline components on machines--planter seed meters, automatic header height control systems on combines, etc. Many shortline manufacturers actually RECOMMEND using online parts catalogs rather than messing with printed publications.
It can be frustrating to shuffle through the pages of a thousand-page parts book in search of a single little part. It can be annoying to click through fuzzy parts pages posted on the internet. But that's what your parts person does every working day, all day long, and why you become his or her best friend when you walk into the dealership with the part already looked up, with the correct part number in hand.
If you really want to see a happy parts person, call ahead and check to see if they have the part on hand. Nothing makes a parts person happier than to have a part sitting on the counter when the customer walks through the door.