Here's how it works--they want you to be in front of them, ready to buy. When you're actually there, your likelihood to do the deal goes up 10,000%. When you're just fishing on the phone they're not likely to take you seriously.
So figure out a reasonable price--keep in mind a Ninja 300 probably has an 8% margin--and write in on a piece of paper. Go into the dealership and ask if they'll give you that price. If they will, great. If they won't, walk. There are about 17 billion Kawasaki dealers in California at last count.
No negotiating required! If they say no, but let's talk about it, they will want you to fill out a credit app, etc. Don't do it! Tell them you'll write a check. The goal is to get you to start thinking payments, not OTD price. "What do you say to $89 a month?" is what they'll say. "Just sign here, and we'll see if we can do that. I have to talk to the sales manager." He has you sit in his little cubicle, looking at the snap-on tool girl over his desk, for about 20 minutes as his sales manager talks about the Warriors. He then goes back to you and says, "we can do $159 a month, plus a free Bell helmet! Just sign here!"
After a few hours of that shit, you'll be happy to pay an extra $500 or $1000 just so you can get the fuck out of there and start riding! So be ready to walk at any time. You'll be amazed at how quickly they cooperate when you get up and head out.