Sorry, but the detail necessary for this is far too much for this web site.
There is a basic process that is followed in all cases.
If you can master these principles you can work most of the details out on your own.
Never forget the definition of a trigger point. A place in a muscle that hurts more than it should with firm pressure, but begins to dissipate if that firm pressure is maintained for up to 60 seconds. Question: Who can feel the pain?
The best control is the patient (you if you're doing self care). If you are working on someone else admit and tell them that you can't feel the pain and need their direction to be effective. In patient care I worked for years with the patients quickly (within a few minutes) learning to say two words. "Yes" meant I had the right spot. "Okay" meant it was beginning to clear (not go away, but simply reduce noticeably). Thereafter, I could let my hands do the work while I could talk of other things or even carry on other conversations with other people. I knew the professional information, but I was simply a tool. Describe the following to them so they will know how to direct you.
First is the amount of pressure to apply. The pressure should be enough to elicit a pain response which is strong but tolerable. The intensity of that pain should be felt as definitely more than it should be in similar and nearby locations on the body. The character of the pain should be of a sharp pain, not a dull achy pain. That is important. The localization of the pain should be fairly point specific with a radiating or spread out area surrounding it.
When treating another person the pain should begin to reduce, become more localized, and or change away from a sharp pain to a less intense ache. This should happen within 60 seconds at the most. If it doesn't, either you are on the wrong spot or the patient doesn't understand the instructions or it's NOT a trigger point. Repeat the instructions and try to move a 1/2 inch or so around it. Keep in mind that bony prominences, underlying scar tissue, nodule, and some pathologies can mimic the increased pain but WILL NOT CHANGE as described. Treating a suspected TP longer than 60 seconds or the patient trying to get rid of all the pain only begins to bruise the underlying tissues that no longer have the support of the knotted muscle tissue.
How much area you treat is up to you. In professional practice I found that one limitation was the time element allowed for professional billing (usually 15 minutes). Another consideration is how the body may react to multiple and diverse areas undergoing change. Doing too much TPT can actually increase generalized pain. Another factor is what you're treating - the primary TPs or secondary ones in the radiating area. Generally, one body area is usually sufficient in a given treatment session. What is a body area? That you'll have to learn from thought and experience. From experience I found that most patients usually only needed from 5 to 20 minutes.
After the above, the most important information, understanding, and experience come from a thorough and understanding of specificd muscle structure and location AND the principles of neurology. Knowing that a particular muscle originates here and inserts there will give you the area to consider when looking for TPs. Knowing the specific muscle function will give you insight into which muscles are affected by type of causative actions. Knowing the neurology of pain transmission AND muscle control will give you point to focus on in different pain patterns.
Yes, details. The basics are enough to start for self care and non-professional care. To become a master needs the rest.