Specialty shops
A good tea shop gives you three things no website can: the smell of the dry leaf, a brewed sample, and a person who knows where the tea came from. Green tea is the category where those matter most, because freshness cannot be photographed.
Ask one question first and judge the shop by the answer. When was this processed? A shop that keeps green tea in a sealed tin inside a refrigerator can tell you the month. One that keeps it in an open bin on a warm shelf cannot, and the tea will taste like it.
Smell the dry leaf before you taste anything. A fresh green tea smells sweet and vegetal. A tired one smells flat, closer to hay than to leaf. The nose catches staleness faster than the palate does, and it costs the shop nothing to let you try.
Then taste it brewed the way it will be brewed at home. Ask for 3 grams in a small pot at roughly 80 °C rather than a mug of boiling water. Boiling water will make almost any green tea taste harsh, and it hides the difference between a good leaf and a poor one.
Online
Online is where the range is, and it is the only realistic option if you want a specific garden or a specific picking window. The trade is that you are buying on description, and the description is written by the seller.
The listing detail that actually predicts quality is the picking date, not the grade. Grade describes sorting and appearance; the date describes how much aroma is left. A listing with neither is a listing you should skip, whatever it says about the region.
Packaging tells you the second half of the story. Vacuum-packed or nitrogen-flushed bags arrive close to how they left the factory. Kraft pouches with a zip lock do not, and a green tea shipped loose in a paper bag across a hot summer will arrive duller than it left.
Transit temperature is the part nobody lists. A parcel that sits at 35 °C for 3 days on the way to you loses more aroma than a week on a cool shelf would. If you are ordering in midsummer, pay for the faster shipping or wait for a cooler month.
Check the returns policy before the price. A seller who accepts a return on an opened pack has something to lose by sending old stock. One who refuses is telling you to take the risk instead of them.
Markets and direct
Tea markets work differently, and green tea is sold there in a way that surprises people used to buying from shops. Stock is often loose, prices are negotiable, and the first price quoted to a stranger is not the price.
The real advantage is tasting before paying, usually sitting down. You can compare four or five greens side by side in 20 minutes, which is more comparison than a shop will usually give you. Bring a note of what you paid last time so you have a reference.
The real risk is provenance. A market stall can call any flat leaf Longjing, and in a busy market nobody checks. If the price is 10 percent of what a documented West Lake lot commands, the leaf is from outside the protected area, and that is fine only if it is priced that way.
Buying direct from a producer has the same upside and the same risk in a quieter form. A grower in Zhejiang or Anhui will sell you last month’s leaf at a fair price, but you have no one to appeal to if the parcel is not what you discussed. Start with a small order.
The practical mix
No single channel is best, and the split that works is boring but reliable. Buy the tea you drink every week online, in sealed packs, from a seller who prints the picking date. Spend the larger sum in a shop, after smelling the leaf first.
Use markets for exploration rather than for supply. They are the cheapest way to find out whether you prefer steamed or pan-fired, or whether a particular region suits you. Once you know, buy that tea from somewhere that will sell you the same lot again.
One rule holds everywhere: match the quantity to how fast you drink it. Green tea in good storage stays close to peak for about 6 months, and an open pack loses aroma faster than that. A 1 kg lot bought cheap is not a bargain if half of it goes flat.
If you only remember one thing, ask for the date. Every channel can tell you where a tea came from. Only some can tell you when it was made, and for green tea the date is the half that decides whether the tea is worth buying at all.