Where to begin
How it works
There are many reasons that people can be so easily convinced of psychic powers, and its all about how the mind works.
Confirmation bias is the tendency of people to remember, and focus on things that confirm and reaffirm what they already believe. While at the same time they will tend to forget, and ignore things that go against what they already believe.
Also most people, especially Americans, and double especially younger people, all believe that they are unique. They often feel that few people truly understand them. The truth is closer to us all being very similar, we have far more commonalities, than differences. This is easy for the reader to exploit, because the subject may not realize just how common their own experiences are.
Homework
The most important thing about successful cold reading is homework. This means more than just reading, it's about studying people.
Watching, listening, and recognizing patterns in everything people do. Commonalities in speech, topics of conversation & behavior patterns. The more you study people, all people, the more you can draw on when the time comes to perform.
Where and/or when
You should only perform readings where you are comfortable. So it's up to you.
It may be a good idea to start off small. A small group at a party may be a good place to perform a random reading.
It is suggestible to be in a quieter, more intimate situation for the reading. This will allow you to hear each other, as well as remove distractions that may make it more difficult to read your subject. Also being in a more private environment may let your subject be more comfortable, and open.
Again, it's up to you, just be mindful of your location, and how it can help or hinder a successful performance.
Choosing a mark
Choosing a subject is extremely important, it is one of, if not the, most important factors to pay attention to.
A good subject will be receptive to the reading, and give honest feedback to the reader. Someone who believes psychics are real will usually be a great subject.
However, someone who is cynical, or just in a sour mood will make for a difficult read. Never be forced into reading someone who you know will be too difficult to read.
By request?
Eventually, if people know you can perform readings you will get requests to perform it. If you feel comfortable, go ahead.
But be wary of poor performances. If you are not prepared, or off your game, you will be less likely to give a successful reading. This isn't the end of the world, but it may make you less confident in the future, and confidence is one of the most important attributes for success.
Also be careful of traps. Occasionally someone may wish to prove you wrong. They will intentionally mislead you, or mock you. This is one of the reasons it is important to not misrepresent your purpose. But you can protect yourself by always trying to control the circumstances of a reading.
Maintain the mystery
It may be helpful to maintain an air of mystery about your skills. Performing readings before the same people too often will make it easier to detect the similarities in the readings.
Mentioning vague magical sounding terminology, and "sciencey" sounding words are very common tricks to add a false feeling of legitimacy to readings.
If possible using props both adds a false mechanism for divination, and also gives a way of diverting attention while you formulate your next move(i.e. staring intently at a persons palm, or closing your eyes while holding a piece of jewelry)
Anything that feeds this mystic can be helpful.
Practice
Practicing can be the hardest part to a new cold reader. Finding people to casually read is a difficult proposition.
The best advice this author can give is to perform short readings at social gatherings with acquaintances. This way you may know a small amount about a subject first. These "Warm Readings" can open the door, allowing you to get comfortable reading deeper information about the subject with an increased chance of success.
And don't be afraid to fail. The worst that can happen is that you get practice at excusing away the misses, which is just as important as making hits.