Word of mouth, basically. Or searching for something that I need.
What I hate most about advertising is it just shoves everything in people's faces and makes people think they need this and that. I find myself somewhat immune to ads (as much as one can be I guess), maybe I just programmed myself to ignore them growing up in early internet days. But it's so obvious the large effect that ads can have on most people.
I find out about new and cool stuff generally from peoples comments on sites like here, reddit etc. If you have a good product, word of mouth is generally pretty damn good. Or coming across something from searches for a specific need.
I just can't think about anything that I needed and found out from a standard advertisement in like.. any recent memory. Maybe I'm the outlier here.. obviously ads must work well enough but I hate them with a passion.