I usually weigh my teas, though if I get very familiar with it, then I'm comfortable eye-balling it (balled oolongs are especially easy). And one gram of tea per one ounce of water is my general starting point for teas with which I'm not familiar, and I usually tweak from there.
That's the nice thing about weighing -- it gets your eye trained and your taste buds calibrated to the results. Once you get used to how things look and taste, you can stop using the scale, if you prefer (of course, you could do the training without a scale as well; it just might require more testing... fortunately that involves drinking more tea...!).
I had the same problem with Adagio samples, though... given the way that I brew most teas, the samples would usually last me 2-3 sessions (vice the 5-10 that they say).