How many shirts have I passed up because they don't have button down collars. If you ride a motorcycle, button down collars are a must. Button down collared shirts, in general, always look neater than those without buttons.
A simple solution to the problem for shirts without button down collars is to sew them down.
Lay the collar down flat against the shirt and pin in two directions.
Needle down in the corner of the existing seam stitching and take about 4 -5 stitches, then reverse back to your beginning point at the corner; needle down. Spin the collar about the needle so that you will be going forward on the other side of the collar stitching. Take 4 - 5 stitches and then reverse back to the corner.
Clip the threads and done.
Here's another shirt. I didn't have the exact red, so I used a thread that matched the button thread.
Love this solution.
If you like this idea, but still want the look of buttons, you can apply a non-functioning button instead which will save the time and hassle of making a buttonhole. The problem, of course, is to find a complimentary button.
Hope it helps,