The cornerstone of aromatherapy is the essential oils. Essential oils are the plant extracts, which have different therapeutic effects upon the body. When you are first learning about aromatherapy, the most difficult time you will have will be how to purchase the essential oils.
The first place you might check for essential oils is your local health food store. This is a good place to begin your research, but not necessarily the best place to purchase them. What you want to see are oils that are packaged in dark glass bottles. Avoid any oils in plastic or clear glass. Light can change the therapeutic properties of some oils, as well as shorten their shelf life. Essential oils can also be great solvents, so plastic is not the best container for these oils. Check the price on the essential oils, they should not all be the same. If they are, do not purchase from this vendor. Some oils are very inexpensive to produce, such as eucalyptus or orange and those will normally cost much less than patchouli or rosemary.
Are there samples available to smell? Different countries of origin can produce different odors in essential oils from the same type of plant. You may decide that you prefer a Brazilian orange to a California orange, for example. Ask about the origin if it isn't indicated on the label or shelf signage. Then check the stock on the shelves. Beware of bottles that are dusty or if the labels look worn. This is a sign of old stock and you won't receive all the benefits of that oil during your aromatherapy sessions.
Check the labeling carefully. You want to make sure that you are purchasing only essential oils. If you see the words 'perfume', 'nature identical' or ' fragrance oil' on the bottles, there is a good chance that these oils are combined with some synthetic agent, which is fine as long as you aren't expecting a true aromatherapy therapeutic result from them.
Another alternative to shopping locally is to purchase essential oils on the internet. There are a great number of online shops that cater to the aromatherapy world. Some only carry the essential oils themselves and others have everything from books to carrier oils to diffusers. This doesn't mean the quality is good here, either. What you want to do is ask if they have free samples first. Be prepared to pay a shipping fee for the samples and only ask for them if you are seriously considering purchasing. If no samples are available, you can purchase a set of oils in the smallest size possible to test. That way you aren't buying a large quantity of an oil that you are not happy with.
Above all, never be afraid to ask any questions of the place you are purchasing your oils. Essential oils are considered to be precious and you only want to buy from a knowledgeable company. Getting the best quality essential oils will give you a superior aromatherapy experience.