Foraging for Food - Part One, An Introduction to Foraging
Foraging for Food - Part Two, More Foraging Tips and Techniques
#1. Time to visit the Library or Book Store
You should try to find a good book on the topic of medicinal plants. You should be looking for a book that is both comprehensive and covers the region you live in. eg. Ontario, Canada.
I also recommend that the book be well illustrated so that you can easily recognize the plants in question.
There are plenty of books on this topic, so really a library will be your best bet for becoming an expert on the subject in a hurry. Borrow every book on the subject and then start reading them from cover to cover.
A lot of what you do with respect to learning about medicinal plants will ultimately come down to how much you can research on the topic and remember.
#2. Keep a Notebook on Medicinal Plants
As you reading and researching, take notes of which plants you think you might be able to find locally and which have useful properties you would like to use. Some you might decide you just want them as a herbal tea, others you might find useful for sleeping, for getting rid of headaches, etc.
Remember, you cannot remember everything so you might as well take notes.
#3. Learn how to Properly Extract the Medical Ingredients
Don't just eat the plant. That is stupid and even dangerous as some medicinal plants have parts of them that are toxic. What if you are supposed to eat the cooked root of the plant and you are eating the leaves instead? You have to learn which part of the plant is actually useful, how to extract that part of the plant, and how to prepare it in a manner that makes it taste better and works more effectively.
eg. When was the last time you saw someone eating chamomile flowers raw???
#4. Learn how to store the medicine
Some plants will rot over time so you need to figure out a way to safely store it so it stays "fresh" and useful to you. If it rots, molds, falls to pieces then it is useless. It might need to be preserved in honey, extracted and ground up with sugar into a pill, or any number of means to keep it fresh and useful. You might even decide to store it as bags of tea - in which case keep your medical tea away from your regular tea, you don't want to drink the wrong tea by accident.
#5. Start a Medicinal Herb Garden
You don't have to forage for everything. In fact, if you know you are planning to use a particular plant again and again a good solution is to plant it in a garden and grow it for future use.
Having the plants handy in the garden means you will be able to grow as much as you need, prepare it all and store it - and while starting and maintaining the garden is extra work and requires space, you will garner so much more from it than you would normally get from foraging alone.
Plus you can grow additional plants that are just for eating, not for medicine. So Win-Win.