Its also immensely helpful if you can go into a meeting knowing what you want. As a good team member, you will still listen to and consider the opinions of other members of the team, and you will consider compromises and concessions. But the more you rely on the professionals to tell you what you think, the more likely you are to agree to things that are not really in your childs best interests. Put your solution or suggestions out there, and let the burden be on them to tell you why or why not, and to offer alternatives.
To mentally prepare for what can sometimes be a challenging and emotionally wrenching discussion, it may help to do a lot of reading about your rights and successful strategies. One excellent Web site for this is Wrightslaw, a treasure trove of information about special education rights and advocacy. But my personal favorite source of IEP-girding inspiration is an essay called Play Hearts, Not Poker, which outlines the sort of collaborative but assertive attitude that I think offers the best chance of IEP success. For more ideas on IEP meeting prep, read my article "Before You Go to an IEP Meeting."
Next question: What should I bring to an IEP meeting?