The best advice that can possibly be given to someone starting out in the fascinating hobby of coin collecting is to "buy the book before you buy the coin". Not doing the necessary research before diving in could prove to be a very expensive mistake.
You do not want to turn your potential fascinating hobby into a potentially frustrating nightmare by failing to understand first principles of what you are getting into. A little bit of research now can save a lot of heartache later.
One often advised method of starting is simply to collect the coins currently in circulation. This can give you a great introduction without involving any risk whatever, as you can take the coins and spend them if you decide the hobby is not for you. You can, however, learn an enormous amount by studying these current circulation coins, their marks and features and comparing them to the reference book you have hopefully bought!
Once you have started collecting the coins currently in circulation, you can broaden your horizons and move into other areas. Hopefully, coin collecting will not only prove a fascinating hobby, but also a great chance to meet like minded people and make new friends.
The most obvious place to find collectible coins is in a specialist coin shop, which exist in all major towns and cities and even in some villages which are antiques and collectors centers. These shops are often run by people with extensive knowledge and experience and can be an extremely valuable source of knowledge, help and information, as well as obviously a great source of coins themselves. You are very unquestionably to pick up a bargain this way, because the dealers will have intimate knowledge of catalog prices, as well as the prices coins can realistically fetch in the open market. What you will be able to do is source many rare and unusual items, by asking these specialist dealers to search them out for you.
Specialist coin dealers are also regularly found at coin fairs and shows. The big advantage of this is that there will be multiple dealers all together in the one place, allowing you to shop around for the exact stock you want and compare prices.
Many coins can also be found at events, which are not exclusively for coin dealers, such as general antique fairs, flea markets and craft shows. As these are not specialist events, you need to take extreme care in making sure that dealers are not just offloading problem stock such as marked or damaged coins. On the other hand, it is also possible to pick up bargains from a retailer who does not specialize and just happens to have picked up coins as part of a general lot.
You can also buy coins from mail order dealers, although in this case you will have to be more careful, as you will have no opportunity to examine the goods before you buy them. In this case it is absolutely imperative that you make sure that the mail order dealer has an adequate returns policy. There have been far too many cases of coins being graded too highly by unscrupulous dealers, or even coins with serious defects being sold to unsuspecting newcomers to the hobby. Make sure, if you are inexperienced, that you get the opinion of someone you can trust and return the coins to the dealer if they are not as described.
Of course there are now many coin dealers on the internet offering near instant payment and dispatch, but again you will have no opportunity to examine the coins before you are charged. Again, make sure there is an adequate returns policy.
A newcomer to coin collecting would be well advised to stay away from specialist or general auctions and from direct dealing with other collectors, unless those collectors are well known to him as being trustworthy. Start slowly in the hobby at first and expand as your knowledge grows.
Do, however, join a local club if you can possibly. Meeting like-minded people and making new friends is certainly one of the great benefits of any leisure pursuit. Getting hold of a good book and joining a local club will be your two most important steps in gaining knowledge quickly, avoiding being exploited as a newcomer and being able to enjoy your hobby as quickly and effectively as possible.