Button-down shirts are great and versatile. However, if you are not wearing a tie and there are no buttons on the collars, you can often look like you are going to fly away with airplane wings around your neck.
This is a simple, inexpensive and quick way to use magnets to create collar stays that will keep the collars on your shirt from looking like you are "cleared for take-off".
There are some folks selling magnetic collar stays for a small fortune ( http://www.wurkinstiffs.com/power-stays/6-2-5-power-stays.html
). You can achieve the same objective with stuff lying around the house for free. I did.