Jane Espenson is a really successful TV writer with a blog about being a successful TV writer. Her tips range from life-changing lessons to common sense stuff that seems so obvious after she points it out you wonder why you never thought of it yourself. There is one repeated phrase she uses that I think applies to more than just TV writing. Here she explains it:
There is always another joke. This is probably the biggest lesson of comedy writing. No matter how much you love a joke, even if a particular joke was why you decided to write a certain episode, there is always another one.
I think this applies to far more than jokes. There is always another idea. There is always another way things can work. Don’t hold onto something out of fear that nothing will be able to replace it. There is always another way.
She also has a few articles on the process of writing in the “Works” section.