I have noticed that I often stay in the familiar circle with my votes, although I would like to support new or rather unknown users. (For this purpose, I find this tool quite useful.) Also accounts like @driveforkids, @nosdos or @steemchiller who works tirelessly on steemworld.org - are great.
So I think a mixture of quality, encouragement, promotion of certain projects and of course personal preferences would be good.