I've attended several classes and panels over the last several years, and there are two things that I've really taken to heart regarding script writing.
The first was gleaned from Gregory Poirier (Missing, National Treasure), who gave a talk at the Northwest Screenwriter's Guild a few years ago.
He recommended that you never take a screenwriting job that you aren't sure you can complete. So, even though this was my first corporate script, I looked at the basics: who I'd be working with, the length of the script, and what the story was we were trying to tell. Factoring in these considerations, I felt confident that I could deliver, and turned in a first draft yesterday.
The other piece that I tend to focus on is listening. I forget who passed on this deceptively simple pearl of wisdom to me, but basically they pointed out that you cannot deliver a good script unless you are really listening to the person/people who are telling you what the script needs. This paid off for me--I think (I hope!)--this week, when I wasn't getting enough info. on what to include in the script.
Maybe you've had this happen to you? You get a stack of paperwork handed to you, with some suggestions, and you have a meeting or two. But even after reading (and re-reading) and meeting (and re-meeting) I still wasn't sure what the point of doing the video was. So I asked a pile of questions, and as a result got an 11 page brain-dump of material.
BINGO.
Let the writing commence.
So, if you're ever offered a script-writing gig, I pass along the same advice to you. Ask yourself, can I write this? If the answer is no, that's okay! Know yourself, and what you're capable of (and know that some projects aren't worth your time.) It's better for you, and your career, to turn down a project than to do one badly.
And if the answer is "yes, I can do this," don't be afraid to listen to what's needed and ask questions. It will pay off for you in the end!