The best best practice as a DPS is to make sure you're hitting something, anything, every GCD you possibly can without missing a beat. Especially because crowd control isn't really an important mechanic in the game so far, even if you're just starting out, it's better to hit the wrong thing (and do at least some damage somewhere) than to hit nothing. If nothing else it will train you to make quick and correct decisions about target selection on the fly when needed.

It's kind of like being Keanu driving the bus in Speed, if you go below 50mph drop a GCD, your computer will blow up and you lose.