If you wish to be kept informed of any bids exceeding yours, enclose a postcard or SASE with your bid.
If you don't know, hunt for writing guidelines on their website, at sites such as Writer's Market or send the publication a Self Addressed Stamped Envelope (SASE) and request a copy of their guidelines.
Many publications now accept e-mail query letters, but remember to include a self-addressed stamped envelope (SASE) if you're sending your letter via postal mail.