Ask HN: What was your most successful Marketing strategy?

I've not had many successful marketing strategies. Some worked really well for what I was trying to do, which makes them successful, but there was a limit!

I needed side-gigs to keep me afloat a couple of months ago, so I posted craigslist ads for odd jobs, computer/printer repair and installation, as well as gutter cleaning. I paid $5 dollars per ad. The most successful ad was the one regarding Installing and Repairing Computers/Printers. I received a number of calls each week for several weeks to come, mostly from older folks who needed help. One guy said he paid $400 dollars for a printer on ebay. For his needs, he could have gotten one at the thrift store for $10, but I digress. Each job was quick and landed me $15-$40 apiece.

I decided to create this Ask HN thread to pick the brains of talented individuals in hopes to shed some light on this very interesting subject. My development skills are good but I feel like a beginner in this realm.