Here's some guidelines from US art blogger Tyler Green. I'm a bit more forgiving than him but agree with most of it, especially keeping image file sizes low and using HTML or even plain text rather than attached Word Docs (I hate the way they create so much garbage when translated to html) and NEVER use all upper-case, even in titles, I just have to retype it!

But don't let it put you off sending me stuff, it easier for me than having to search it out.