How much of a personal injury settlement will I be entitled to? Is it true that if I wait to negotiate a settlement with an insurance company on my own, and then contact and attorney to get more, that the attorney can only charge me a percentage of whatever extra he manages to attain? And not a portion of what I was going to get anyway?

OMG, I hate being asked this question. You and the attorney can work out whatever you want to on the fee. There is no set percentage split, but I would not take on a case for less than 1/3rd based on what you describe. If the lawyer takes the case with the agreement you mention, then the lawyer makes a mistake, will you sue him/her for above the amount he should have negotiated, or for the entire amount? You will sue for the entire amount. The lawyer therefore is taking on responsibility for the whole settlement and what you suggest as a way of determining the fee would not be acceptable in my office. Of course you get what you pay for and I'm sure you can find an attorney who's not very good at personal injury work, but would like to make a quick buck and will accept the terms you propose. After the settlement you'll be writing more questions here asking if you should sue the attorney. You get what you pay for. Good luck with that one.

What you propose is not right. Let's say you talk the insurance company into $9,000 of a $10,000 settlement. The lawyer took over and all you gained was $1,000. Why would any lawyer in their right mind be willing to take a case where he's on the hook for $10,000 of liability for payment of $1,000? And who says your case will settle for anything? You say it was you that got the settlement, but you didn't because you turned down the settlement and once you rejected the insurance company's offer it essentially went back to zero. So there was no settlement after your rejection of their offer. 

Whatever you do get a written agreement on the contingent fee, so that after you settle and the fight is on about what was said, at least we have the written agreement to go off of. Again, good luck with that one.