Analyzing the task at hand, comparing the current task with the previous tasks that were done by the company and then taking the appropriate decision as to how much time would be required. When the PM is new this is how he/she will assign the time for the task so as to reduce the risk but as the PM would be experienced he will know the task at hand, the human resources and their capabilities and hence will be better at assigning the time for the tasks and will be a good planner. This will save time as well as money will be utilized effectively, hence reducing the risk of being late.