I've heard people talk about "department store scopes" or "trash scopes". How do I know what to avoid in a beginner scope? How can I know that I'm not getting something we will be more frustrated with than excited about?
Avoid small refractors and reflectors on skinny tripod mounts. Don't buy from a discount or department store. Don't buy from eBay, CraigsList, or Amazon.
Here are a few web pages with good information on beginner's telescopes:
For more advanced information, read Phil Harrington's Star Ware, 4th edition (Wiley).
You'll get the greatest value for your money with a Newtonian reflector on a Dobsonian mount, such as these:
Buy from a store which specializes in telescopes and astronomy, either locally or online; don't buy from department stores, discount stores or eBay as mostly what they sell is junk. Find your local astronomy club and try out different telescopes at one of their star parties:
I strongly recommend that beginners steer clear of astrophotography until they have learned their way around the sky. Astrophotography is by far the most expensive and difficult area of amateur astronomy.
Many people who buy telescopes have no idea how to find interesting things to observe. A good introduction to finding things is NightWatch by Terence Dickinson (Firefly). A more advanced book is Star Watch by Phil Harrington (Wiley).
@Bradc asked the question as to what scopes to avoid. The first thing to RUN from is ANY scope that states a large "X" or multiplication factor! This is a very good clue that it won't provide useful or enjoyable viewing. It will be small in diameter, the mount will be flimsy. You will be looking as if by a straw! Pointing it will be difficult, it will not track very well. The sell cheap! They are in hobby store windows, and on their shelves. They will only have cheap eyepieces, that are made to be easily made with poor optics and will create distortion. The main lens is full of the chromatic aberrations, or IOW lots of colors that aren't really there. Find someone or some group. See what they are using to really see! They will talk to you and show you what can be seen. You can learn what to look for and what the costs can be expected to be.
Assuming by 'beginner scope' means 'cheap', Cheap Astronomy promotes exactly what it says on the tin, and their page on telescopes is clear about what you can and can't expect do with a cheap telescope, in terms of astrophotography etc.
The Cheap Astronomy podcasts are all excellent but definitely listen to episode 10, 'Your First Cheap Telescope'.