Summarize this article:

Look at the historical performance of your sales team. How many units have they been selling per quarter? Take this number and factor in a rough estimate of the kind of growth you'd like to see. Use this number to determine the quotas you want your sales team to reach.  For instance, your salespeople might have been 25 units a quarter, but you'd like to see 20 percent growth. Set a quota of 30 units a quarter. Setting aggressive quotas can be reasonable, as long as you are prepared for the possibility of scaling back in the future. If you are just setting out and don't have historical data to draw on, research the sales figures of your competitors or similar companies in your market. Managing a team well means having expectations and helping team members meet them. If you want each team member to sell 30 units a quarter, for instance, expect them to do so. Don’t make excuses for underperformers. If, however, many of your team members consistently have trouble meeting quotas, it may be time to review your expectations and create more reasonable ones. Consistent, widespread problems making sales--even among your best workers--is a sign that your expectations are off. Keep careful track of your sales metrics and compare them regularly against your expectations. Make any adjustments that seem reasonable. For instance, if many of your team members seem to be having trouble meeting your quota of 30 units per quarter, try scaling back to 25.

Summary:
Set reasonable quotas. Hold your team accountable for quotas. Review your metrics to keep expectations realistic.