Hi idiotic idiot06
As Lucas42 said, re-using stamps is technically illegal, but many people still re-use stamps if they haven't been cancelled. It's up to the individual to decide whether they wish to re-use stamps or not.
I find the easiest way to stick uncancelled stamps is to firstly make sure there isn't any envelope on the back of the stamp. If there is, soak them in water so the glue from the stamp can dissolve enough for you to soak the paper off. Make sure they dry
flat on absorbent paper or a towel.
For all the other stamps, the flatter they are, the easier they will be to stick onto new envelopes. If you have to, wedge bent stamps under a heavy object to keep them flat.
In order to stick the uncancelled stamps onto the envelope, glue would be your best way to go. Make sure the glue is strong and sticky. I find that some glue sticks work well, but you may find another types of glue suited to your needs.
Put glue on the back of your stamp, making sure it covers the whole back of the stamp. Before sticking the stamp on the envelope, I find it sticks a bit better if you add a bit more glue on the envelope before sticking the stamp on. Just make sure that the back of the stamp and envelope are clean before doing this.
Hope this helps. Happy collecting
nowandagain [rockon]