My favorite are the pistons which say, "Fits AT, CT, DT, RT." By the time you get an AT piston in an RT jug, you better have some rings like the planet Saturn!

Sorry, I meant look at the pictures on CMSNL and old pictures of original bikes, brochures etc to familiarise yourself with what the parts you need actually look like - you will likely find as many listings showings parts that do fit your bike, but are listed for something else, as parts listed for your bike, but which don't fit. I often don't even bother putting the model in a search if I'm looking for a part, I just put "Yamaha speedo", "Yamaha mudguard" etc. and then look at the photos for what I know is the correct part. I agree with Steve F that patience is needed!