Never done it before

How shall I remove the old grout? Some kind of Dremmell type thing or with a fine chisel?

I have all white tiles dunno what size Do i need sanded or unsanded grout?

Any tips for a neat job?

 

You can buy a thing in B & Q that is specifically for removing the old grout. Its like a scraper thing

 

Or you can buy a product called grout revive, which cleans up the grout lines without the need to regrout.

 

Ask Sean Forsyth (K5SSY), he knows his stuff