Herbal medicines are dosed according to individual circumstances and also according to traditional knowledge.  Traditional dosage ranges are modified according to the size and condition of the patient and for the severity, symptoms, and particulars of the individual case.  

Self diagnosis and self prescription are advisable only in simple acute conditions such as treating a common cold, occasional indigestion, or minor injury.  Chronic, recurring, or serious conditions require evaluation by professional practitioners of traditional Chinese medicine.

That said, the following information may be useful for those treating simple conditions and without access to professional guidance

Pills: As prescribed or as directed on the label.

Granules: 2-4 grams, taken 2-3 times a day, best on an empty stomach

Whole Herbs: Using a container made of ceramic, glass, or stainless steel (no aluminum, iron or copper) boil 1 packet of herbs in 2-quarts of water or until 2 cups of medicine remain. 

Strain herbs; save and refrigerate for a second boiling. Drink 1 cup in the AM. And 1 cup in the PM. If desired, repeat the following day, using the saved herbs from the refrigerator.

How to Cook Herbs 

The potent odors and flavors of medicinal herbs are legendary. Boiling the herbs and drinking the tea will provide the fullest experience of these medicines.  Here are a few pointers on how to prepare and decoct Chinese herbs.  For more basic information see A Patient's Guide to Chinese Medicine. 

Herbs are generally boiled for 20 - 60 minutes. After boiling the dregs are strained out and the remaining "tea" is taken warm or at room temperature, usually twice a day and most often on an empty stomach when possible.

Boiling times for a formula are averaged according to the composition of the formula. For example, flower and leaf will yield medicine in 5-20 minutes. bark, and branches take 20 to 40 minutes; Roots take a bit longer and shells and minerals must cook for at least one hour and are usually pre-boiled in advance of the other herbs in the formula.

A few herbs that contain volatile oils, like mint or citrus peel, must be quick-boiled for only 1-5 minutes lest they lose their valuable volatile oils. These herbs are added separately to the boiling mixture just before completion. There are also a number of herbs, such as Cordyceps, SAN QI, or Indigo powder that are not cooked at all but are added to the strained decoction.

A Few Tips

First, while cooking herbs, ventilate the kitchen. This stops the odor from deterring you (and your family). If you find the taste of your medicine disagreeable, hold your nose when you drink your herbs. This eliminates almost all the taste. Drink your herbs lukewarm or at room temperature. Hot liquids must be sipped slowly. If you hate the taste, you'll want to drink it down quickly. Cold liquids have less taste but may be hard to digest.After drinking your medicine, chew a few raisins or place a drop of lemon juice on your tongue to eliminate any aftertaste.

Herbs can be absorbed up to 30% better when taken on an empty stomach. Allow at least a half hour after taking herbs before eating or taking additional medicines. There are some exceptions. If your medicine proves difficult to digest, try taking it with food or after eating. Some doctors believe that formulas designed for the upper body should be taken after eating. Some medicines are best taken with other liquids such as wine (injuries or vascular problems), broth (to aid digestion of the herbs), or salt water (messenger to the Kidneys).

Tinctures are best diluted with a small amount of water to reduce the caustic effect of the solvents they contain. Heating these liquids can evaporate some solvent. Use a small amount steaming hot water to dissolve water extracted granules (powdered). The hotter the water, the better these dissolve. If the water is too hot, however, you'll be forced to sip your medicine. So let it cool or add a little cold water. I briefly stir in an ice cube. Instant cold without a lot of extra liquid to swallow.

Milled powders can be boiled, taken as tablets or steeped as a draught (teabag).