Harvard Law School attorney Stu Rees did his thesis on comic strip syndicate contracts. Stu represented me and several other cartoonists and helped change the way syndicate contracts were written and negotiated. Here's a link to his thesis.
The Graphic Artists Guild keeps an eye on what types of contracts illustrators are having to sign. It offers a good resource for understanding contracts as well as offering some real-life contracts as examples. GAG Contract Monitor.
The Authors' Guild has Negotiating tips for nine typical contract clauses.
Famed Illustrator C. F. Payne has some strong thoughts on Work-for-Hire agreements. While hard to avoid, WFH agreements remove an illustrator's legal authorship to his or her work. You're not just selling rights, nor simply the original art, but your very claim to authorship. Not a new article but an important one, especially since Payne's career has skyrocketing (at least compared to mine!) since he wrote this article, indicating it's not necessary to sell out in order to make a living.
Our best luck is with clients who do not have a boilerplate contract. Oftentimes clients who do have a contract have "borrowed" it from someone else, rather than having an attorney draft one for them. In any case, it is better for the Illustrator to have his or her own boilerplate, often referred to as a Letter of Agreement (see GAG Contract Monitor above). This allows the Illustrator to have more control in the negotiation process, and creates a better opportunity to explain the terms for usage of rights.
It is best to grant usage rights as specifically as possible. For example, Exclusive North American print rights for one year in March 2007 issue of Passing Classical Gas magazine. After that point, all rights revert back to you.
Limit the number of unpaid revisions to one or two. Chances are this will halve your annual workload and double your income for the year! I'm only slightly exaggerating.
How do you know if you've negotiated a good deal? If afterward you don't feel like you just screwed yourself. Never be afraid to say No and ask for what you are worth.