Do not tuck in your polo shirt. Polo shirts are casual, and are not meant to be tucked in.
While we are on topic, the length of a polo is crucial. It should hit at your waistline and just hide your belt...not your thighs. Also, if your sleeves are touching with your elbow you need to size down. The sleeves should hit halfway between your shoulder and elbow, which gives you a chance to show off those biceps you've been working on all winter.
Enjoy the beautiful weather,
Yours in style, Style Blogger