While I am certainly not trying to vote for witnesses on the top, some of them certainly are there because other people must share my opinion. I try and vote very organically by considering people that I just organically come across as I peruse Steemit. If I like what they are doing and how they are benefiting the community and they ask for a witness vote then I certainly give them my vote. That being said at any given time I'm only voting for 8-10 witnesses... I am not sure that is the best way, but I'm not going to vote for people I have not reviewed just to hit my quota of 30.

My best advice is just to interact with the blockchain and discover who is worth your witness votes.