Step 1
Don't assume that all old coins will be in very poor condition. If you are buying coins you can expect such coins to be in respectable condition, even if it is over 500 years old. Of course, as the age of the coin increases, the condition, if very good, will add more value.
Step 2

Find something to hold your coins. This does not mean that you have to buy fancy coin holders (although this would keep them in better condition). Coin holders can be fairly cheap or you can use an old shoe box or peanut butter jar.
Step 3
Store in a safe place. If you are buying expensive coins, invest in a safe-deposit box and containers that will not destroy the numismatic value of your coins.
Step 4
Decide what you want to collect.
- You might like to collect foreign coins or your home country's currency.
- You might like to collect smaller denominations or larger denominations
- You might like to collect circulated coins in coin folders to try to complete a series such as your own life span.
- You might like to collect uncirculated coins which have been available in the United States since the 1950s.
- You might like to collect proof sets which are uncirculated coins prepared especially for collectors
- You might like to collect silver proof sets which are very beautiful (more affordable than gold) and there value will increase (or decrease) as the value of silver increases (or decreases).
Step 5
Ask friends and relatives if they have old change, and then, ask if you can have it or offer to buy it, depending on what feels appropriate.
Step 6
Check with your local bank of financial institution. Many will sell you rolls or bags of coins at face value.
Step 7

Expand your collection by going to coin expos. You can also visit your local coin dealer for buying coins and almost all the time there's a cheap coin bin that is suitable for kids and adults alike.
Step 8
Note that some people advise collecting coins out of pocket change. Once a modern coin has been in circulation, it is typically only worth its face value, although there are notable exceptions.
Step 9
Understand grading of coins. Grading coins is often difficult and there is a tendency for people to over grade their coins. Also beware that the US grading system rates more highly than the UK one, for example a US graded "mint state" might not be as good as an "extremely fine" coin in the UK.
Step 10
Note that the US grading system also has trouble with grading hammered coins, those which were made by hand (with a hammer and hand held dies) as opposed to milled coins (which are made by machine).
Step 11
Coins can be a good investment. Coins have been growing in value faster than the rate of inflation, as well as the interest rates paid by banks. If you buy and sell carefully, there is money to be made.
Step 12
One of the best ways to "buy and sell carefully" is to read the book before you buy the coin. There are many books on the market. First the catalog with basic information and price estimates. Then there are books available on individual series (the Lincoln Cent), types (ancient coins, mint errors, gold coins, tokens and medals etc.) There are books on grading coins which is important to determine value. Books are available on most any topic of coin collecting or Numismatics as it is more formally known. Knowledge is how we tell the difference between a rare coin and one that is common.