My ratings will usually be based on multiple tastings. Green and oolong teas are generally 3 grams of tea in 6 oz water for 1 minute. Black teas are 1.5 grams of tea in 6 oz water for 3-4 minutes.
My numerical ratings are all based on how much enjoyment I took from the tea. Since I prefer blacks and oolongs, they will receive higher scores. I also give a couple of extra points to decafs, just because I can drink them in the evening without staying up half the night. I don’t dislike flavored teas, but find that they lack the complexity of finer teas.
90-100 = superior, worth a high price
80-89 = Excellent. Will buy again
70-79 = Good tea, but probably won’t buy
60-69 = Nothing really wrong, but…
Below 60 = Wouldn’t drink again