Sealing Natural Stone tiles

Hi,
Is it best to seal natural travertine tiles before or after grouting?
I'm worried that if sealing before the grout will not stick to the edge of the tiles very well.
Also what is the best drill bit to drill natural stone with, or is there a good adesive I could use to put mirror and radiator brackets back up?
Thanks

Seal before grouting otherwise the grout will stain the tile and you won't get the marks out, then seal again after grouting.

Travatine is quite soft, for screw holes a normal masonary bit will be fine, use it without the hammer action until you are through the tile. Tap the rawlplug below the tile to reduce the risk of splitting the tile.

Jason

Thanks for the help