The first is the compulsive use of the passive voice/tense.
Definition: When you place the object of an action in a sentence as the subject of the sentence.
The Problem: While passive is not always a grammatical error, it is a less energetic way of phrasing activities - it is also a lot less clear, concise and attractive. It also denotes a lazy writer and a lack of careful authorial attention, which is not a good image to give your readers!
The Allure: Passive sounds so dang fancy! I have a very bad impulse to pretend that I am Jane Austen when I write, which generally leads to an over-abundance of antiquated sentences and convoluted constructions. While Jane Austen was a master of the narrative and characterization, there are much better gurus to look to for grammar and editing inspiration. (I love the passive verb clauses, as you can see in this post.)
The Fix: Round upon round of editing until I weed the little buggers out and clean up all that sloppy, purple prose! With the passive, recognizing I have a problem is half the battle, and nothing can be done but re-reading and tweaking. Sadly, auto-check can't really be relied upon (or, I guess I should say, auto-check is not reliable...?). The only thing to be done is to edit it by hand with an eye towards active rather than passive. sigh.
Still not sure what the problem is?
If you are still confused, I feel your pain. I don't always recognize the passive as problematic, either, when I am reading. It has only been a serious of resounding "No! Bad Writer! Bad!" corrections from editors that has forced me to read specifically for the passive.
Perhaps a common example will help...
The road was crossed by the chicken.
Naturally, we know this sounds weird. We usually say this as "The chicken crossed the road."
Why? Because placing the doer instead of the object of the action in the driver's seat of the sentence is a much more engaging and clean way to say it. Putting the horse in front of the cart, if you will.
After she was shoved down, Suzy cried.
This sentence fails to tell us who shoved Suzy down, as it is missing the doer. "Tommy shoved Suzy down, making her cry" is better.
Try this one:
These truths are held by us to be self-evident...
That certainly lacks the sparkle of "We hold these truths to be self-evident" doesn't it?
Exceptions to every rule...
Sometimes, the passive is not only perfectly fine, but preferable, making it even harder to edit for them.
Baby Kate was born at 8pm today!
Clearly, Baby Kate is the star of that sentence, and there is no one else that need be mentioned as important as her. "Dr Phil Winthrop delivered Baby Kate today..." is not only needless but a lot less interesting. Even Dr Winthrop would likely agree that he's much less important than Baby Kate at her own birth.
This is what Strunk and White say:
The need of making a particular word the subject of the sentence will often... determine which voice (active or passive) is to be used.
However, the section on "Use the Active Voice" ends with a typical Strunkian assertion to "omit needless words," reminding us that:
...Brevity is a by-product of vigor.
And so it is.
There are many much better explanations and discussions about the passive online, so I won't go on. But, suffice it to say, this is a problem with which I continue to struggle, though I am improving. My early writing would likely make me cringe with all the passives, but I am seeing fewer and fewer of them all the time, except where the sentence demands it. I keep several how-tos bookmarked for easy reference during editing, so I can keep my mind on track.
The quick trick:
1) Re-read with an eye to subjects and objects.
2) Consider the meaning and where the emphasis needs to be.
3) Revise to make sure the correct thing/person is driving the sentence.
4) Repeat again and again until you are sick of the term "passive voice."
Good luck is wished... I mean, I wish you good luck!