I know marketing is a matter of testing what works and what doesn't, tweaking things, then running with what works until it stops working.
I enjoy hearing about the entire process and that includes the failures.
One of my first efforts was when I was a teenager. I was trying to sell vacuuming services to offices. I didn't have a lawnmower, but I thought I could just go door to door doing the same pitch as friends who mowed lawns used. I must have went to 50 different stores and buildings. I didn't get a single client. Nobody seemed to take me seriously. I think the logistics and reasoning of letting a teenager into empty offices alone late at night also played a role. Trust may have been an issue as well. If a kid is cutting your grass in daylight outside, you or somebody else can at least keep an eye on him if you wanted.
Seeing people's reactions to what I was trying to do eventually wore me down and made me stop. It was a good lesson in rejection though and helped me get thicker skin, (very slowly, but surely).