How can I make my cookies fluffier instead of flat?

How can I make my cookies fluffier instead of flat?
9 Tips to Remember

Use Real Butter and Keep It Cool. The low melting point of butter may be what makes your cookies flat.
Use Shortening.
Chill Dough Twice.
Use Parchment Paper or a Silicone Liner.
Measure Precisely.
Use Fresh Baking Soda.
Use Optional Add-Ins.
Buy an Oven Thermometer.

9 Tips to Remember
  1. Use Real Butter and Keep It Cool. The low melting point of butter may be what makes your cookies flat.
  2. Use Shortening.
  3. Chill Dough Twice.
  4. Use Parchment Paper or a Silicone Liner.
  5. Measure Precisely.
  6. Use Fresh Baking Soda.
  7. Use Optional Add-Ins.
  8. Buy an Oven Thermometer.