Rarely play an open unless there is no other option.
+1 My bass teacher tought me to avoid open strings because you don't have as much control over your playing when you use open strings. It's harder to keep them from ringing out. I will use open strings once in a while though, but only when it's just more practical. And of course you want to be able to use your low e, so that's the only open string I play all of the time.