Once again, research is your friend. Often a magazine or journal will have submission or pitch guidelines posted on their website. If so, follow them. If not, I think that a quick, polite email asking if they have submission guidelines is appropriate.
It’s a very good idea to read a couple of back issues of the magazine or journal that you’re thinking of submitting to. That’s the best way to find out what type of writing they publish. It might seem time-consuming to do all of this research, but really, it saves you time in the long run—making sure that you’re sending your writing or pitches to the most appropriate, suitable publications, and doing it in the way they prefer.