I don't understand potency with regard to 6x, 12x, C, M, etc. is what David asked us in our Hmedicine.com forums. We referred him to our single remedies guide but we are going to attempt to answer this question in a little more detail.
The more dilute a homeopathy remedy is, the stronger it is and the higher the number or potency. A less dilute remedy is not as strong and has a lower number or potency.
To answer David's question, a list is below from the least strong homeopathic remedy to the most strong homeoapthic remedy.
Remedies from least strong to most potent
1X would be the least strong remedy.
30X Middle Strength
CM+ Strongest remedy
X verus C - This question often confuses the novice to homeopathy. An "X" potency is a remedy diluted 1 to 9. 1 part remedy to 9 parts alcohol. The "C" potency is 1 go 99, 1 part remedy to 99 parts alcohol. X and C are fairly interchangeable since both have been potenized the same number of times. If you can not find a 6X of a homeopathic remedy, the 6C would be an okay substitute.
Low potency homeopathic remedies(1X-30C) are generally used to treat acute illness, whereas higher potencies homeopathic medicines(200C-CM+) are used to treat chronic complaints.
Most people treating acute illness should generally start with a 6X potency. If they feel that potency is not strong enough, they may move up to a 12X or 12C. They may also decide to move up to a 30X or 30C for even more strength.
Most chronic complaints should be treated with a licensed homeopathic physician. 200C remedies and upwards should generally not be self prescribed. Homeopathic physicians for chronic compliants may not necessarily prescribe a 200C or higher remedy. Starting with a high potency may overshoot the problem. The homeopath may start the patient on a 6X. The homeopath may move up to the 200C or higher potency if they feel more strength is necessary in treating the chronic condition. 200C, 1M and higher are rarely taken as often as low strength homeopathic remedies.
A Guide For Taking Homeopathic Remedies Washington Homeopathic Products.
Complete Guide to Homeopathy. Dr. Andrew Lockie and Dr. Nicola Geedes.