Based on the priority and dependency, assign user stories to a Sprint totaling upto the capacity of the Scrum team. For example, 10 User Stories with story point ranging from 5 points to 21 points and totaling upto 90% of the team capacity, which in this case is 90 Story Points. I usually keep a 10% buffer to accommodate bugs and uncertainties. If no bugs or errors surface from current sprint or previous sprint, and team has free resources, the team can always pick up a story from next sprint and be ahead of schedule.
I noticed that while working on current sprints, a number of times bugs and errors surface regarding functionality built in previous sprints. These bugs and errors were simply missed by QA to capture in that sprint. I would not calculate story point for bugs to include in current sprint since they really do not belong to the current sprint. This is the reason why I started reserving 10% resources to accommodate bugs.
Now instead of emphasizing on calculating the amount of hours required to complete a user story, the emphasis should be on estimating the time remaining to complete all User Stories in a Sprint. This calculation can be displayed in a graphical manner using Burn Down Chart. For example, if there are total of 100 Story Points to be completed, Burn Down Chart will show in a point in time that there are 45 Story Point remaining on Day 3.
The burn-down chart displays remaining work in the sprint backlog. Burn-down chart is updated every day to provide status on the progress of the sprints. During sprint planning each member picks tasks from the sprint backlog and updates the remaining hours for tasks by the end of the day. This updates the burn-down chart every day, shows the remaining work required, and also provides a trajectory which shows whether the goal of completing all tasks on time will bet met or not.
This method of managing story points provides allocates just enough work which can be accommodated by the capacity, provides daily updates, and gives a good estimate on whether the tasks are on schedule and will be completed within the current Sprint.