Firstly, the handy tips to do it by preparing polishing solutions from things available in your kitchen.
1. Take a mixture of half cup baking soda and three cups of warm water and apply it on the surface of your worktop. Wipe off the excess liquid and buff with a soft sponge. This will help remove any stains and deposits on your worktop’s surface.
2. Prepare a mixture of 1/4 cup of isopropyl rubbing alcohol, water and a few drops of any mild detergent or liquid dishwasher soap. Fill the solution in a spray bottle and squirt it over the worktop surface. Rub the surface in slight rubbing motion to bring back the shine on your granite worktop.
Ready made kits available in market to polish granite surfaces.
3. Buy a commercial non-abrasive granite polish and sealant from a hardware store. Clean you granite worktop to make sure no residues or any liquid is on the surface. Apply polish to the area and buff with a soft clean cloth. After applying polish on the surface, proceed by using sealant on the granite as an added protection. There are also ready made granite maintenance kits available in the market to guide you how to polish the worktops.