I've been doing consulting work all in all now for about 13 years for myself and various organizations. The worst consulting jobs I've had the misfortune to be part of are ones that aim to serve an agenda other than creating a good solution to an actual problem. So far, these have fallen into the following broad categories:

• Consulting where you are required to choose from a set of products defined by your employer rather than by the customer to serve a "partnership requirement" or revenue goals.
• Consulting where you are actively attempting to create a product for general resale for an employer via one or more less general consulting engagements.
• Consulting where the management of your employer or customer mandates the use of one wholly inappropriate technology for "strategic" purposes rather than immediate technological or business purposes.
• Consulting where the point is to spend down some sum of money rather than to create a real solution.

The best thing about working for yourself is that if you're sufficiently alert, you can just avoid any of these traps, which tends to make both you and your customers happy. The best consulting jobs are invariably those where you solve a real problem for a real customer without any middlemen or alternate agendas. One hallmark of such an engagement is that everybody understands what you're trying to deliver. Another hallmark is one and only one customer who has a vested interest in keeping things on track. These kinds of jobs usually produce happy customers who are willing to give shining references and future work. OTOH, it's difficult to get (or even accept) good references from victims of consulting engagements that fit into the above four categories.