Where can I buy puzzles?
For brand new puzzles, there are many stores to buy puzzles from, all over the world. Checkout the Puzzle Shops wiki for a list. There is also the Puzzle Shops forum with a vast amount of puzzle shops.

You can also find other users on the forum selling used puzzles in the Buy/Sell/Trade area.

What kind of cube should I get?
Search around the forum, look into reviews, buy a few a test them. You can find reviews of most puzzles in the Puzzle Review forum.

How do I make my cube better?
Make sure you've lubricated the puzzle. Search the forum for mods, lubricants, and common problems to make your cube better. Checkout the Puzzle Hardware wiki for links to many helpful resources.

What is the difference between X puzzle and Y puzzle?
Search for the specific puzzle you're looking for on Google images, or search some online shops for descriptions of the exact features of each puzzle. It is probably best to read reviews if you're wondering why one puzzle is better than another.