How to evaluate existing supplier and how to evaluate newcomer vendor ?

The  suppliers, wether existing or newcomer, are to be evaluated on the basis of their performance in terms of prices offered, jobs executed in the recent past, timely deliveries, quality of goods/services delivered, settlement of claims, litigations, existence of facilities and manpower, financial resources, market reputation etc etc. The same set of evaluation factors are applicable in both cases. However, the difference is thto be at in case of suppliers doing business with the company, the data of said criteria is easily available and also reliable. However, in case of newcomers, such data is a bit difficult to obtain and reliability is also not of that degree. Aother aspect to be kept in mind while evaluating existing suppliers is that we need not to re-invent the wheel and we may also make use of the past data avaialble with us.