I like to get suggestions for videos to watch, things to read, music, but (perhaps because my tastes are not that mainstream), it doesn't provide me with much I can use. This goes for ads, too. I like to see ads that are relevant to me - new music, new products, equipment - but it doesn't show me these often enough.
So YouTube / Google should let me provide it with keywords - a list of things I'm interested in at the moment. It could send me a reminder to update parts of my list every month or so ("Name, are you still interested in blank?") or offer related keywords I might be interested in, which I could check off in boxes or not.