For about a month after getting my kilt I wore t-shirts with my kilt because I pretty much only wear them casually and I never tucked them in. I recently realized not only is it more comfortable to tuck in a t-shirt but it does look far better than letting it hang (plus my shirts tended to rest right behind the sporran which looked ridiculous) so I have to agree with the other guys on tucking it in.

I only wear some basic shoes with mine and then if I wear hose also I usually keep it up, but with boots, again, I'm with the rest, scrunch 'em down.

And have fun!