QSLing
When QSLing make sure your QSLs have all the information a station needs to confirm your contact. Also make sure your QSL has the information needed for the recipient to use for their own award chasing. Try to make the information as easy to read as you can. Keep the information on one side of the card so the recipient doesn't have to flip it back and forth in a search for the information. Include such items as your name, address, callsign, county, grid, zone, island name, and IOTA number. QSO information should include callsign of station contacted, date/time of contact (UTC), band, mode, and signal report. Keep your cards "normal" postcard size.
Do not just put a stamp on the QSL and mail it like a postcard. Mail machinery tends to damage QSL postcards. Put them in an envelope. You should also include a SASE (Self Addressed Stamped Envelope). If mailing outside of the U.S., put "U.S.A." under your address. Ensure you include sufficient return postage or funds to cover the postage. To presume it is "only" 39 cents and the person receiving the QSL should make "the last courtesy of the QSO" and send you a QSL at their expense is rude. If it is "only" 39 cents to you, then you should have no trouble doing YOUR "last courtesy of the QSO" and providing a SASE with sufficient postage/funds. If you live in California or Texas you may get one card a month, if you live in North Dakota or Wyoming you may get 10 cards a day. The person you are QSLing may be living on limited retirement funds or may be out of work. Never assume someone else has the funds to pay for your hobby.
Some examples of why you should put your QSL card in an envelope:
Look where the postmark lands on these cards! Not always easy to read.
This card came in a bag with a note of apology from the Post Office. I taped most of it together. Some of it never arrived. Not the best looking card to hang on the wall!
The post office wasn't sure whether to "Return to Sender" or forward this one. Needless to say, both sides of the card are pretty marked up.
The odds of this happening are greatly reduced if you put it in an envelope. Besides, how else can you send that "last courtesy" SASE unless you enclose it in an envelope?