Full details of preparation are available from the download section of this website. In brief, it is necessary to thoroughly clean the paving you will be coating, preferably with a jet washer and ensure that all grease, loose materials, oil stains etc are removed.
The paving should then be allowed to dry thoroughly (full depth, not just the surface). If you are sealing block paving you will then need to apply sand to the joints and we would recommend that you do this on the day that you intend to seal to avoid the sand getting damp in the interim.
Any loose sand should be carefully brushed off the surface before sealing.