[jyl]

Various considerations.

New or used. New bikes depreciate hugely. There is no benefit to getting the very latest model. Bikes are very mature technology. Last year's model is fine. Heck, a 2012 model is fine.

Fit. Critical. Bike shops often don't fit customers well. You have to know what size you need. Obviously so with used bikes too.

Weight. I'm a weight weenie, to some extent. But realistically, as long as your road bike weighs 20 lb or less, it's okay for typical recreational riding. Lighter bike, lighter wallet.

Components. You'll be looking at the standard road bike component set. Double chainrings, front derailleur, 9+ speeds (cogs) on the cassette, rear derailleur, integrated brake/shift levers. Probably caliper brakes, maybe discs. In all likelihood, Shimano. All tiers of Shimano work okay, but Tiagra looks and feels cheap, DuraAce and Ultegra look and feel niiiiice. Similar comment about the various tiers of SRAM, Campagnolo, etc. For $2K your not in electronic shifting territory.

Frame. Steel and aluminum are sturdy and you can confidently buy a used one with a bit of inspection. Carbon I don't know about. I might lean to buying those new.

Type. Simplistically, there are race, sport, touring, cyclocross. If you plan to load up with heavy panniers for a long tour, you want a touring bike. Race and sport are a matter of degree, but some sport models have a high head tube, which makes it hard to get the bars a good distance lower than the saddle, if you wish that aggressive a position. Cyclocross bikes are getting very popular, they can take wider tires than race bikes which makes them versatile.

Features. The main one I'd care about is eyelets on the fork and dropout, for fenders and a rack. If you plan to have those things.

Aesthetics. Very important, of course.

So, start with these questions:
1. How tall are you and what is your bike inseam (google it), and how flexible are you (can you touch the ground with legs straight, can you put your palms flat on the ground).
2. What kind of rides do you want to do - 50-100 mile hilly rides, short flatter rides, fast group rides, solo commutes, only ride on dry days, ride in all weather, etc.
3. Do you, or are you willing to, ride with clipless pedals? If "no" then fuggeaboutdit, only hipsters ride road bikes with flat pedals and only retro fogeys ride road bikes with real toeclips/cleated shoes.
4. Do you want one bike that you'll stick with for a long time, or do you want to buy a starter bike to ride while you learn what you really want? You can always sell the starter or turn it into the rain bike.
5. Are you going to work on it yourself and have tools/are mechanical, or do you own one tool and it's a butter knife so you'll have the bike shop maintain it?