The smartest thing you can do is take the time to learn your "actual waist size". I am floored by the amount of guys that don't know there pant measurements. It's easy. I have videos for you to watch so you don't even have to read anything.
Follow the size charts.
If you buy something in the future just take to time to measure. It's worth in the end. A lot of times you are wearing the wrong size anyway.