Most people are casual coin collectors, however some folks get the bug and get serious. They want to get complete sets or just get the rarest coins possible.
Collecting coins can be good investment, but you need to be sure you don't make bad decisions. The best way to avoid mistakes is to educate yourself. One good way to do this is to have good reference book and to cross check them with each other. Check prices with multiple dealers and keep up to date with recent magazines and web sites to be sure you have the latest coin information and most accurate coin information available. Don't believe everything you hear.
Once you start getting valuable coins you will want to protect them. You will likely pay a bit more, but you will want good protection for your coins. One way is to get hard plastic holders that are designed specifically for protecting coins. Another way is to get coins that are already in airtight containers. If you buy coins this way, do not remove them from the container.
You will also want to handle your valuable coins with care. Dings and nicks and wear on a coin will reduce its value. Even touching a mint coin can ruin its value. So handle your valuable coins with the utmost care. If you have to touch your coins, only touch them on the edge. Make sure your hands are clean. Only put coins on clean and soft surfaces. The best way to keep your coins perfect is not to handle them at all. So only take your coins out of their protective containers when absolutely necessary.
Even if you get more serious about collecting coins be sure you have fun.