Write the minutes. Take someone with you to write them if you can't write/speak/listen at the same time. Listen very carefullt oa ll that is said. Don't do too much talking.
Bear in mind the following:
TAC are supposed to be a chance for all professionals involved in a child's life to get together, be across developments in that child's life, and make concrete plans to meet the needs of that child. Note the 'concrete plans' bit. It isn't a big chitchat free-for-all. Every professional should end the meeting with something to do - some action to take that will improve your child's lot. Have a look at this to get a better idea of what TACs are supposed to be.
TACs are also usually a chance for the parent/school to assign a lead professional to co-ordinate all support for the child. In theory, this should mean that one professional takes responsibility for chasing up the others to make sure they do what they need to do. In practice, this doesn't work very well in my experience. Unless the parent has some reason that they cannot co-ordinate support (ie. mental or ill health, poor literacy etc that mean that they cannot chase up appointments, make sure people are sticking to doing what they are supposed to do), the parent is always a child's best advocate. I insisted that I was assigned 'co-ordinator' . You can do the same if you wish.
TACS usually go hand in hand with CAFs. A CAF is a great big long document which outlines all the needs and issues of your child, which professionals are involved, what their role is etc. In theory, this is supposed to ensure that all your child's info is available to all professionals (usually on a computerised system), that you don't have to constantly retell his/her 'story' to new professionals that may come on board, and that professionals involved in supporting your child are kept abreast of developments in his life. They are extremely helpful in a small minority of cases. In many cases, they are used instead of a more time consuming and costly statement (in my experience). If a CAF is proposed, get the proposal and reasons for suggesting a CAF in writing. Then you can consider whether you think it is a useful step or just a time wasting exercise to appease you and make you hold off going for a statement.
Finally, remember to use it to your advantage. Make a list of all of your issues and questions and ask them. You've got everyone around a table, so use the opportunity. I used our first TAC to get CAMHS to say what they thought the school were doing wrong. They would never have done it in writing or an official report, but I teased it out of the CAMHS guy and then BAM - it was out in the open, the school couldn't argue with it and I had recorded it all in my minutes
Good luck.