What coins should I collect?

Whatever types you like! There are many different specialties:

It's often easiest to start with the coins of your own country but it can be fun to collect world coins, either in general or from a specific country. Either way, you learn about the history and culture of the country through its currency.

Some people like ancient coins, or Revolutionary coins, or coins from any other time in history. Also, others try collecting series of coins (all of one kind of coin from a decade, or all the years it was minted). A lot of people start with trying to build up decades of a coin in mint condition.

The more expensive collections include gold and silver coins. These are very challenging to collect, and generally aren't attempted by beginners.

This is the term used in coin collecting for anything that's made of metal, usually round, but not legal tender. Elongated (or "squished") souvenir pennies, medallions, tokens, and commemorative coins fall into this category.

My advice- Start with any interesting thing that comes across your path. In time you'll become more selective as you develop some areas and don't find much in others, or as you discover your interests.

Once you know what type(s) of coins you want to collect, you'll want to keep a few things in mind when buying an addition to your collection:

Oftentimes in coin shops or antique shops there will be bins or boxes of the same kind of coin. If they're all the same price, that doesn't necessarily mean they're all of equal value. For example, many antique shops that don't specialize in coins will throw all of one type of a coin in a pile and let you pick one, thinking they're all the same. Sometimes there will be several nice examples of the same coin on display. Here are some qualities to look for that will help you pick the better example out of the crowd:

Check to make sure that the all the writing that should be on the coin is present and clear. Avoid coins where the lettering is faint or completely worn away. Look closely at the designs on the coins- can you see fine details like the feathers of an eagle or the folds of a robe?

The reason these coins are in the bargain bin is most likely because they've been circulated. Since they've been passed on from hand to hand, jingled in pockets with other coins, dropped, etc. all of them will have dings, scratches, maybe even some chemical scarring from bad storage. Look for coins that have no chemical scarring (pits, corrosion, etc). Some nicks and scratches may be acceptable, especially on the parts of the design that are raised. Deep gouges or distracting marks are to be avoided. Try to find one with as few obvious marks on it as possible. If you really want to examine it you could use a magnifying glass but if the coin's in the bargain bin then whatever is acceptable after examining it with the naked eye should be enough.

Toning is the term for tarnishing or discoloration. Believe it or not, some kinds of toning will actually increase a coin's value. A blue tone on silver coins is considered desirable, and an even tone on copper coins is acceptable as long as it isn't so dark that you can't make out the details. Sometimes toning helps to accent the details and make them easier to see. As long as the toning isn't uneven, so dark that it obscures the design, or just plain ugly, then it's not a reason to reject a coin. For example, a shiny coin can be weakly struck, meaning the press didn't bear down hard enough so there isn't much detail. On the other hand, you could have a toned coin that was nicely struck so the toning brings out the details more than usual. A lot of this one boils down to personal preference.