Define the criteria for best path selection of a router?

Routers select best routes based on the criteria Longest Prefix match (Routers select the routes with longest match to the destination address), Adminstrative Distance (if a router recieves multiple routing protocols it will install the lowest distance in the table) and Metric (if the router receving the same route several times then it will check with the metric and select lowest .)

the route with the lowest value for cost is the main criteria for the best path. off course the OPSF will calculate that based on bandwidth