There are probably hundreds of signs that the writer of that script I'm screaming at is an amateur. But today, I'd like to give a mere 50. Most of these may seem like common sense, yet you'd be amazed at the sheer number of projects plagued with these issues. Some of them may make you worry about your own work. But hey, at least you'll know for next time and you'll be one step closer to making sure your work is at the highest of professional standards.
The following is in NO particular order and covers a broad range of script issues.