Whether you're a first-timer or a seasoned drinker, these rules apply:

• Buy in small quantities. Matcha degrades quickly once exposed to air.
• Store it airtight in the fridge, away from light. Don't keep it next to your coffee beans.
• Check the harvest date before checking the price. A fresh harvest from last spring beats a six-month-old 'premium' blend.
• If you're in NYC, visit shops that let you smell the matcha before buying. Many Japanese grocers and specialty tea shops are happy to open a tin.
• When in doubt, ask the staff when the batch arrived. If they can't answer, that's a red flag.