Suggesting someone just for preference is a bit hypocritic, especially because I am also a witness.

If you want "hints" about how to choose them, I can give you my end...

Usually, I choose by:

• Seeing that the witness is around (quite very important)
• Not constantly failing blocks (otherwise means it does not have a way to maintain the chain stable). If witnesses have problems with their nodes, then they should disable, fix the problems, and once all good, re-enable. - Do not confuse this with a witness having a great total of failed blocks. That might mean nothing.
• It's helping the community in some way...
• It's not asking for money in exchange for votes (if they are, they are not helping the security of the chain)
• If providing infrastructure for the blockchain, like public RPCs, etc... (and if in the top 30's) then this becomes a second priority on the list, otherwise, it's a big plus but I don't see it as mandatory, especially because it becomes costly to maintain without a bigger plan.
• Helping around in general
• etc...

There are lots to consider, but I might just have made an "out of my mind" list... anyone can make their own "choices"...