Inexperienced players have little to think about when they're drawing; the consideration is never there to get out of line (i.e. raising, etc.), so they'll already know their one move is to call. Why Hollywood when you're anxious to see the next card off the top? On the other hand, and examining the hand by contradiction, let's say you have a set or top two on that board; wouldn't you be considering raising? Wouldn't you at least stop to think about what actions you should take to get the most money in the pot while you think you're ahead?
In other words, the quick call is almost always a drawing hand. This tell should be cautioned, though, because a player can sometimes show up with a weak top pair, or even second and third pairs hoping to catch up on the turn.
As you become a more experienced player, you should recognize this tell fairly easily, and be aware that you may be doing it yourself. Try to spend the same amount of time on all decisions, so as to not give away timing tells such as the one described above.