One thing I find irritating is when I have to squint to see something properly. No one wants their photographs to be fuzzy (unless you're going for a deeply important effect, in which case I'll be quiet now). No one likes blurry printing. It's the same when we write - we need our writing to be focused. I find it helps me to keep the following in mind:
1. Establish your reality. Every book has its own reality - it's in the present and taking place in Paris. It's in the past and taking place in North Carolina. It's on the planet Zuron. Your characters are a vital part of this reality. Make them real.
2. Remember the main plot is the one that gets the most attention. Subplots have a habit with demanding the spotlight, but the spine of your story isn't a subplot; if it is, I'd suggest you need to do some thinking as maybe your subplot is the main plot.
3. The plot moves forward logically. Step one usually leads to step two, sometimes step one and a half, occasionally step three. It does not jump to step twenty seven.
4. Characters stay 'in character'. Characters come in all shapes and sizes and abilities - but one person can't be everything. If someone has an intense fear of heights, the odds of them voluntarily going bungee-jumping is small. Of course, they could be trying to impress someone, or trying to fit in with their crowd, in which case bungee away. But watch it. Know your characters' strengths and weaknesses and then respect them. Growth is great - but no one is capable of a complete personality transplant.
5. The ending really is an ending. I don't believe you have to tie up every plot line, but I do believe readers want (at the least) the main plot completely resolved. Subplots' conclusions can be definite or hinted at - but don't leave readers hanging. Leaving readers wanting more is a completely different kettle of fish.
The best advice for me is from "Alice in Wonderland": "Start at the beginning, go to the end and then stop." I take it to mean you may not write the manuscript using this method, but once all those revisions are done, that's the way it should read.