How can I learn professional magic tricks like the ones you see on TV?

Go to the library or the bookstore and find some good books. Then you have to study them, and practice what you learn. A great beginner book is Mark Wilson's complete course in Magic. (Available at Amazon)

Often you can find a local club dedicated to magic. There are benefits and drawbacks to these clubs, and different clubs have different rules. Some are completely open, while other require you to prove your ability to perform at a certain skill level before being able to join.

Also many of these clubs are connected with larger organizations, such as The International Brotherhood of Magicians.

www.magician.org

And the society of American Magicians

www.magicsam.com

There are other organizations outside the States also.

There are also a lot of websites out there selling a lot of magic tricks, but it is best to learn from books, and videotape/DVD, though many will argue against the latter, at least for beginners.

Magic is not a collection of little secrets, but a complex form of entertainment. It is a mistake to think otherwise. Many tricks are very complex, and the secret would actually be very boring to the average person. And a true magician will practice for hours to master a 30 second trick.

There is no substitute for reading a good book such as The Royal Road To Card Magic which is a real classic.

There are a few good websites which offer free tuition for the beginner magician. One of the best I have found is http://www.goodtricks.net

You may buy books and tricks on magic stores.
Talk to some other magiciand that you may know.

And visit free sites like http://www.magicsir.com for free video tutorials.