I posted on this recently and Bill V gave some good suggestions. See the link to my original post!

Here is a link that might be useful: Tile Sealing Question

On Bill's advice I used the 511 Impregnator and have never had a stain.

Thank you both :)

Where do you purchase sealers for marble? Do the big box guys carry them (Lowes, HD)?

Also, how often do you need to seal marble? We will have honed carrera on our kitchen island and honed crema marfil in a bathroom and want to make sure I take good care of them!

yes, they do, and you shouldn't have to seal them more than once every couple of years.

I bought my 511 Impregnator at HD.