Page Margin Best Practices epub->mobi

[BKh]

What is the best css to use for page margins in an e-pub that will be converted to a mobi?

I do all my reading on a Kindle and so I am accustomed to the margins being set by the device. But I want the e-pub's that I create (in Sigil) and then convert to mobi (using Calibre) to look good on most devices. My understanding is that e-pub devices don't usually have a default margin. At the same time, I don't want fixed margins to end up in the mobi I create.

So, suggestions on what the best css is to include in the epub along with a good margin size? Also how do I make sure that Calibre removes them in the mobi?

Apologies if this has been covered elsewhere.