Before purchasing a new washbasin, you should make a checklist of all the important dimensions. The list should include the dimensions of the old washbasin, the distance of the washbasin drain from the wall and the position of both angle valves. As a general rule, you should take accurate measurements rather than rough estimates.
It is advisable to obtain a complete installation kit from the DIY store for the installation work that will be required later. It consists of fixings, hanger bolts and collar washers for protecting the ceramic surface.