Below the information you want about making herbal teas, but please take good note of the following warning.
ALL herbal teas are medicinal doses of a drug/medicine. One cup of herbal tea per day (any kind) is a medicinal dosage for an adult. DO NOT regard herbal teas as beverages, any more than you regard headache pills as confectionery. Herbal teas should only be used to treat specific ailments, and preferably only after consultation with a doctor or medical herbalist. Why? Because many herbs interact with other herbs and conventional medications; because some may be contraindicated in certain pre-existing conditions (even the most popular culinary herbs have some effect on the heart, blood pressure, circulation, and other vital functions, and may make a condition worse); most have side-effects (lemon balm, for instance, can cause severe night-sweating); many should not be taken during pregnancy (including mint tea which stimulates the uterine muscles); and because a doctor can monitor your reactions to the drug. Individuals may show allergic reactions to herbal teas. Don't forget that a herbal tea is quite a concentrated dose of the active components in the herb. If you are taking ANY herbal medicine or supplement, you MUST inform you doctor, especially if you are due to have surgery - that includes dental surgery. you should stop taking herbal medicines and supplements at least 2-4 weeks before surgery, or else you could have problems with anaesthetics and haemorrhage. Herbal teas are generally NOT suitable for children under 12, except on medical advice. A medicinal dosage of a medicinal tea for children is 1 teaspoon.
Please don't ignore this advice. I've been growing and researching and writing books about herbs for many decades, and I know it to be very sound advice. Grow herbs by all means, and learn how to use them wisely, but treat them with the utmost respect because they are nature's DRUGS. They shouldn't be swilled down willy-nilly.
Off the soapbox now, and the info you wanted, with some of the ailments the herbs you want to use will treat. BTW, you can make a herbal tea of almost any herb, but it's important to know which part(s) of the plant to use. In the case of lemon balm (which is closely related to mint) and the mints, it's the leaves and sometimes the flowers.
A herbal tea is made by 2 methods - infusion or decoction. Fresh or dried herbs may be used in roughly the same quantities.
To make an infusion: An infusion is made from softer parts of the plant - the leaves, stems and flowers. Pour boiling water over the herb and leave for 5-10 minutes, as in making ordinary tea. While steeping, the container should be tightly covered. Usual quantities are 15-30g of herb to 600ml water. Strain off the liquid and discard the solid matter. To make one cup, use about a teaspoon of the herb. Usual dosage is 500ml per day divided into 3-4 doses. Do not store an infusion for longer than 24 hours.
To make a decoction: This method is suitable for bark, roots and seeds. Allow about 30g of the herb to 600ml water. Pour the water over the herb, soak for 10-15 minutes. Bring to the boil and simmer for 10-15 minutes. Cool for 10-15 minutes. Strain off the liquid through a cloth or fine sieve and discard the solid matter. A standard dose is the same as for an infusion. May be stored for up to 48 hours.
Lemon Balm: Used to treat: Anxiety, depression. Panic attacks. Digestive problems caused by stress. Cold sores. Over-active thyroid. Cuts, insect stings. Fever. Colds and flu.Shingles. Circulation. Antibacterial. Insect bites and stings. Catarrh. Eczema. Fatigue. Nausea. Teething. Toothache.
Peppermint/spearmint: Used to treat: Digestive problems, diarrhoea. Headache, migraine. Respiratory infections. Aroma inhaled to combat shock. Morning sickness. Mumps. Irritable Bowel Syndrome. Diverticulosis. Prevent gallstones.