One of the big no-no's in writing is the over use of "Being Verbs":
is, am, were, was, are, be, being, been.
You can edit these out by using the "Find" tool in Microsoft Word. After putting in a search see if there is a better verb you could use in it's place. Sometimes rewriting the entire sentence helps.
It's hard not to write these words into our writing because that's how we talk. I have to make a concious effort to write without them.
Action verbs are a much better choice. My writing sounds better when an action verb has replaced a being verb.
Anna saw. Replaces- Anna was seeing.
Robert showed. Replaces- Robert was showing. or Robert was being shown.
Lisa learned. Replaces- Lisa was learning. or Lisa was being taught.
You get the idea.
We also need to watch the overuse of "Helping Verbs":
may, might, must
do, does, did
should, could, would
have, had, has
will, can, shall
Someitmes they are necessary but when used too much they lose the reader.
This list is for myself more than anyone else, but if it helps you too than great. :0)