Improve your chances of getting photos published
Try to pick half a dozen of your best images and concentrate on the ones best-suited to the magazine and its readership.
If you're photographing a car restoration project, the readers might tolerate one or two 'arty' shots, but mostly they'll want to see that the door decal (for example) has been positioned exactly the right distance from the sill.
And if you're submitting a manipulated landscape shot to Digital Camera, say, then it won't hurt to include the 'original' shot too and maybe a couple of different variations, so that the editor can see how it might form an interesting story.
This is an important point. You might be used to thinking of photographs as single, static images, but magazines are actually about 'stories'.
Take a look at the mechanics of magazine reproduction too. Full-page photos often need space for headlines or other information and pictures used across a double-page spread need space for the 'gutter' in the middle.
While you might not submit pictures with this kind of space initially, it wouldn't hurt to shoot variations with this in mind.
You don't have to stop at supplying images either - why not write the words too? You may be surprised to learn that pitching articles is a much easier route into magazines than photography alone.
PAGE 1: Practice Patience
PAGE 2: Making the right approach to editors
PAGE 3: Improve your chances of getting photos published
PAGE 4: Common mistakes when trying to get photos published
PAGE 5: What will you be paid?