Competition submission guidelines—much like all writing guidelines—are determined by whoever is in charge of that particular competition. Because sponsors of the events vary, the submission process and formatting vary as well. It’s most important to follow their guidelines.
For example, if Contest A asks you to single space, you single space. If Contest B asks you to double space, you double space. If Contest C asks you to quadruple space and add emoticons to the end of every paragraph, you do it. The law of the land is determined by the competition sponsor.
It’s true that some competitions won’t specify all the particulars, and you may be left scratching your head. When in doubt, you can follow these general guides when submitting for writing competitions:
• Double space (except for poetry and scriptwriting)
• Use a standard font, like Courier, Times New Roman or Arial
• Be sure your name and contact info is at the top of the submission
• Cut and paste in body of e-mail. (Don’t send as an attachment unless specifically requested)
• Avoid using smart quotes (the curly quote marks). You can turn off the function in Word.
• Keep in mind that bold, italics and other formatting often don’t come through when pasted into e-mails, so avoid them if possible.
Again, most competitions have their own guidelines and it’s key that you follow their requests. But when in doubt, these specs should help answer your basic questions.