Passive negotiating. So you're not one who enjoys conflict? In fact you avoid confrontation of any kind? You don't want to hurt anyone's feelings or take advantage of anyone. You're a giver -- not so good at receiving? You're a helper, not so good at being helped?
Here's the two things you can do that will not create the dreaded possibility of tension and disapproval, but give you a chance to add dollars to your paychecks.
Some negotiations require action on your part. Documenting, comparing, estimating, promising, etc. Other things are more passive. you want the least amount of negotiating besides saying "OK" (which is simply no negotiation at all!) consider these two passive techniques.
1. Be quiet when it's time to be quiet. You can still be an agreeable person, just don't agree right away! Use "The Flinch." When it comes time -- and it will come time to do this no matter how nice you are -- to talk money, simply let them talk. You don't need to break in; don't need to counter offer; don't need to do anything proactive, or even reactive: just be quiet. When you hear their offer, repeat it and say "Hmmm." Think about it. You will probably get a raise on the spot.
2. Ask "What's the best you can do?" You don't need to argue, present your evidence, make a case, etc. You don't need to say "no" to the offer you received or re-negotiate terms or cover fine pits. You don't need to demand more money or even ask for more money. You won't push them outside their comfort zone. Simply say, "Wow, thanks for your offer. I look forward to starting. And I'm not a very good negotiator, so I prefer to leave this up to you -- I trust you'll tell me the truth. What's the best you can do?
There, that's not so hard, is it? Have fun!