For another series of tips on how to submit your nonfiction, check out these tips of what to do and what to avoid.
Some accept periodically. Some accept all year.
Follow the directions. Seriously.
Don't send follow-up emails to the editors (unless and until they specify it's acceptable)
Stop worrying about submission fees
Aggressive and hyperbolic cover letters will NEVER get you accepted. This is art, for gracious sake, not a used car.
Do NOT submit your nonfiction to The Paris Review, The New Yorker, Harper's, or anything else of that caliber. If you're of that level you're beyond relying on web pages like this.
Develop some cred with a bio and work your way up the ranks first
Find an app or program with which to keep track of what, where, and when you've submitted or want to submit to-- or set up an Excel sheet. The more organized you are, the more professional you'll appear.
If you've been submitting to a lit mag for years without luck, your work doesn't fit.