An accepted practice and one I have used from time-to-time, when still cosidering or writing a piece, is the Query Letter.
http://www.essortment.com/all/howtowritequ_rrx u.htm
The above website should answer all of your questions, or you could simply GOOGLE a question such as, "How to write a good Query Letter."
Don't be disappointed if you get no response to your letters.
Good Luck and remember, "Don't let the &%*+$!#~ grind you down." Most writers could wallpaper a block of high-rise flats with their rejection slips.
Been there, done that.........
Old Salt