2. Don’t gather herbs from places which might be contaminated by herbicides/pesticides, lead paint or animal waste. Avoid gathering near busy roads or near railways. It's important to use clean, uncontaminated plant material. A little dust can be washed off if you plan to tincture the plant or use it immediately. Plants intended for drying or infusing in oil should be gathered where they are as clean as possible since it's best to simply shake them off before processing them in these ways.
3. A good rule of thumb for home remedies is if your great-grandmother would have taken care of it at home, with knowledge and good sense you probably can safely too. If you have an injury which threatens life, limb, or eyesight, there should be no question but what you should seek medical care. Use common sense and seek medical care for any serious problem. If a problem continues to worsen or does not improve within a reasonable length of time after you attempt to care for it yourself, seek medical care.
4. Pay attention to Latin names when using herbs. Some plants share the same common name but are not interchangeable for herbal use. This is particularly important when you're learning herbal names from a book and then attempting to identify them in the wild or when ordering herbs from a catalog. Some plant species in the same genus may be used somewhat interchangeably. For example, if you have some mint in a pot, you don't necessarily have to know whether it's peppermint (Mentha x piperita) or spearmint (Mentha spicata) in order to make a tea from it but it can be helpful as the two are used in slightly different ways. Many plants in the same genus are not interchangeable, however, so you need to do your research before making any substitutions.
5. If you are prone to allergies, test a small amount of any new herb on your wrist and watch for any redness or swelling before using internally. Wait 15-30 minutes after applying the herb or herbal preparation to your wrist. If there is no reaction, you can drink a couple of tablespoons and watch for any reaction. Those not prone to allergies may prefer to take a small amount of a new herb (for example, a half cup of tea) and note any reactions.
6. Be aware of special health considerations you may have (pregnant, nursing, autoimmune disorders, medication you are taking) and educate yourself about types of herbs which may not be appropriate for your condition. This is mainly in regards to using herbs internally but there are some exceptions. There are many herbs which can interact with medication. For example, yarrow may interfere with blood thinning agents and with blood pressure medication. Herbalist Aviva Romm specializes in herbalism for women in their childbearing years and is a good source of information for women who are pregnant or breastfeeding. Here is an article by her discussing herbs during pregnancy: http://avivaromm.com/herbal-medicines-in-pregnancy-safety
7. More is not always better! Follow recommendations for herbal dosage from a reputable book, website or herbalist. Please exercise caution and good sense when getting to know herbs. If a resource emphasizes to only take one cup of a particular herbal tea at a time, don't drink a quart! Do your research to know which herbs can be safely taken in larger amounts and which are safe only in small, carefully measured amounts.
8. Use gentle food-type herbs if you are a beginner. This is a good way to get to know herbs with less risk. Herbs such as spearmint (Mentha spicata), chamomile (Matricaria recutita or Chamaemelum nobile), roses (Rosa spp.), lemon balm (Melissa officinalis), catnip (Nepeta cataria), elder (berries and flowers only, not leaves or stems, of Sambucus nigra and Sambucus canadensis) and oatstraw (Avena sativa) are often used in beverage teas for good reason. They are generally safe in varying amounts in most circumstances. Plantain (Plantago spp.) is an excellent herb for beginners for external use.
9. Use the gentlest possible herb in the gentlest possible preparation which is still effective. Teas are some of the simplest and gentlest herbal preparations and I've found them to be surprisingly effective most of the time. There's also no need to use a harsh herb which is hard on the body when something gentle like chamomile will do. Often even external application such as in the bath or as a compress is effective and safer than internal use. It's particularly important to stick with gentle herbs when making preparations for children. There are many herbs which are appropriate for adults which are not appropriate for children.
10. If you choose to use essential oils, please educate yourself thoroughly from a reliable source such as http://www.learningabouteos.com/ or http://roberttisserand.com/ Many herbalists consider essential oils as separate from general herbalism because they are highly concentrated preparations which require special equipment to produce and because they come with special precautions. Essential oils should always be diluted before external use and never used internally, unless under the direct care of someone trained in their proper use.