I can't say that I am very consistent in choosing witnesses... 14 votes spent only.
A witness must be active on Hive. Posting, developing projects, joining events.
I am looking at my votes, and, yeah, I could add a couple of votes for top10 guys... But why should I, they already are on the top... Better to find smaller witnesses to support their passion... I'll try to find someone right now.
Well, there's a reason to vote for top witnesses even though they are already on top.
General approval for top witnesses are dropping. Ideally top20 witness would have 50%+ of general HP approval.
But yeah, finding good motivated rookies is also good strategy :-)