Every couple of weeks or so, a friend or colleague asks for camera-purchasing advice.

“What kind of camera do you use?” is usually how it starts. “That depends on what I’m shooting,” I usually answer.*

Although my answer may sound evasive, it’s actually a statement of fact: No single camera/lens can excel at everything. And because you’ll always have to make a trade-off of some sort, it’s good to know which features are critical to you—and which you can do without.

There’s a list of about 20 questions I usually ask my friends (What are you going to shoot? Which is more important: Camera size or image quality? Do you use manual focus?) … but that would make for a very long—and probably not very useful—blog post.

So instead I’ll offer some online resources that may help steer you in the right direction.

Learn the basics: The photography guides at about.com and Digital Photography School offer some great general advice on buying a digital camera. Digital Camera Info goes one step further by recommending the “perfect” camera for a variety of situations.

Do some research:  Consumer Reports offers an excellent overview, including a helpful rundown of camera types, an explanation of the most common features, and a discussion of the top brands.

Do some more research: If you already have a specific camera in mind, Digital Photography Review can probably tell you about its real-world performance. The site also offers a handy “comparison” feature, if you’re on the fence between two or three models.

I’ll close by offering my personal caveat: Remember that more megapixels isn’t necessarily better. Squeezing more megapixels onto a compact camera’s tiny sensor actually increases image noise (and thus, reduces image quality). Plus, more megapixels also mean a larger file size—which will fill up your memory card faster. Anything between 6 and 10 megapixels is fine for most folks. And anything above 14 megapixels is probably overkill, unless you’re buying a big ol’ SLR and you need the resolution.

Well, that’s all I’ve got. Have some camera-shopping tips of your own? Please send them along.

* These days, my walk-around camera is a Canon G11, or my trusty Canon S3. But when I travel I usually carry my Panasonic GH1 with its versatile 14-140mm lens, or—for street photography—its kid sister, the Panasonic GF1 with its prime 20mm (40mm equivalent) f/1.7 lens. I also have an old Canon 40D that I’ve dubbed “The Doberman” because of its heft—but it seldom leaves the house these days, probably because of its heft.