The first article of this series says that the most common stamps are very chiep and everyone can afford them, they usually remain at the same value. Some of the stamps have high value from the beginning and sometime it grows. Collecting rar e postage stamps is also known as philatelism and it's a popular hobby, even when the postage stamps worth a lot of money. Most old and rare stamps are higher in value when they are unmarked and misprints can worth more.
Rare postage and vintage stamp collecting is a challenge: you need to have a solid background knowledge and to have money to invest. Learn everything you can about the stamps and how they were manufactured in different periods of time, learn about the equipment you could use when dealing with such rare and valuable things.
When you deal with a rare stamp the very first step is to decide how to preserve it best. If it came on an envelope, and you have good chances to happen so, you may decide to keep it on in order not to damage it or that the postage meter mark is worth saving. In such situation you can showcase the entire envelope in the album or cut around the postage meter. In both cases you'll have the stamp still stick on the anvelope.
On the other hand, if you decide it's safe to remove the stamp from the anvelope, don't peel it off. Soak the stamp in warm water for some time in order to dissolve the glue, that will allow you to gently remove the stamp. Use philately tongs made of plastic, don't use the metal tongs (nor your fingernail - I am sure some of you could take fingernails in consideration) to remove the stamp because you can damage its edges. Wear latex gloves to avoid getting the fat (usually known as fingerprits) or oil fron your hands on the stamp. Once you removed the stamp from the envelope let it dry on a flat surface for a few hours and put something heavy on it (like a book) to flat it once it's dry.
Mounting a rare postage stamp into an album is not such uncommon thing, but you need to handle it carefully and to choose your album wisely. Consider the quality of the material when you choose your tools. Mount the stamp into a hinge or (preferably) a sleeve if you don't want to damage the back of the stamp, then place into a stamp album with acid-free pages.
The very important thing is to keep everything as cleen as possible. The dirt is the most important enemy of the postage stamps, even greater than the human error when handling them.