Does anyone have any advice on how to negotiate a good contract when one is offered a titled position?

I'm a lousy negotiator, but I'd recommend that you talk to people who are already in titled chairs, and feel them out for what you should be looking for. Don't ask them what they've got, but just ask them for advice about what you should do. You don't want to push any boundaries.

A few things to keep in mind - there are other things than money, so think about not only what your salary needs might be, but if you've got a very expensive instrument to insure, see if they'll cover that. A parking stall in the garage is a nice perk if you can get it. If you're a principal, you might be able to swing some additional time off, either in terms of not playing pops, or just being able to sit out a concerto on a program on a regular basis. Also consider if you'd like solo opportunities on an annual or semi-annual basis.

I should say that principals are most likely to get perks, not so much the other titled players, but your mileage may vary.

Best of luck!