Choose your clients & projects carefully
2 points:
1: Not all consulting work is good work, for a variety of reasons: the client is a bad/difficult/non-paying/indecisive client; you'll receive a low effective rate; the project doesn't move your business forward (e.g., the client will have no other work for you); the project keeps you stuck working in obsolete technology, etc. Being desperate to pay the bills is a sure way to snag some horrible consulting work--and turn off high-quality clients.
2: Like others mentioned, a consulting business is a business, and since we're reading Tech Republic, we're likely all techies, which also means there's a high probability most of us don't have much experience in marketing & sales. That lack of knowledge is fixable, but it's also one of the main reasons I see people struggling to build a sustainable consulting business (or ANY business).
A couple rules of thumb:
1. If a client can't identify the specific value they'll receive from a project, AND if you can't identify the specific value to yourself and/or your business from a project, then the project probably isn't a good idea. It has to be a good fit for both you and the client.
2. Trust your gut instinct. There's been recent neuropsych research on how those gut feelings are often based on cues we might not even be consciously aware of--cues that indicate that something's out of whack. Just like Mark Miller commented above, listening to our gut and paying attention to red flags can prevent us from getting ourselves into problems.
