I was perusing ye olde Internet and came across this article called "How to Be an Editor's Dream." It has some good advice, but I was also surprised by the number of suggestions that I wanted to add on to, or tweak, or disagree with. Here are some thoughts:

1. Giving more than you promise
When an editor asks for two samples, give her three.
On the other hand, don't give five when she asks for one. Editors are busy people. Submit a few well thought out pitches but don't send a long list of ideas. You'll just clog up email boxes and annoy people.

2. Constantly coming up with fresh slants
An editor likes writers who can reduce her brainwork, and make her look good in front of her superiors by coming up consistently with great ideas.
Don't use all your slants on one publication, however. If you're that good at coming up with fresh slants, branch out, if you are so inclined.

3. Having all the answers
Because an editor's never going to trust you with an assignment unless she's sure you know what you’re doing.
But don't be afraid to ask your editor for help along the way if you need it. Editors prefer somebody who can ask for feedback or direction as opposed to somebody who's faking it.

4. Coming up with clever titles, and great sidebars
Don't assume anything, though: just because you have a great idea for a sidebar doesn't mean your editor will go for it. Gently suggest a sidebar and why it would be good before you work on it. The magazine just might not have room or money for your little extra, plus the editot might think you're being greedy if you always have a little something extra to suggest for every assignment.

8. Knowing the magazine
If you don't want to go broke buying all the prospective magazines, get yourself a reliable Internet connection and visit the magazine's Website.
DON'T visit the magazine's website! The majority of magazine websites I've seen are short on content, unless it's an online publication. Go pick it up from the stands.