Copied from MrBlackPCS here:
http://my.opera.com/negotiate/blog/
MSRP= Sticker(includes Dest. Charge)
Invoice= Can be found on Edmunds.com(include options)
Rebates= Can be found on Edmunds.com
Holdback= Can be found on Edmunds.com
Est Tru invoice= Invoice - Rebates - Holdback
tax= ?% x True Invoice
Tags= whatever your states charges
Low ball offer= True Invoice + tax/tags - $2,000
Target Price= MSRP - rebate or Sale price - Low ball offer / 2 + low ball offer(this is basically the formula I use)
---------------------------------Formula-------------------------------------------
---------------------------------------per request---------------------------------
Confidence is your biggest asset! If you dont believe you are going to pay invoice they will smell your fear like a pack of wild dogs. The car business is hurting right now. Dealers are happy with their "holdback". Its the salesman that are starving. STOP NEGOTIATING WITH THE SALESMAN! Its a fact that the average car salesman only sales 8-10 cars per month. Its also a fact that a "flat", the money a salesman is going to make on a new car sales with no profit(invoice) is $50-$100. So do the math thats only $800-$1000 in commission per month. Thats why dealer are always hiring salesman. Its also why salesman are constantly getting fired.
GET THE SALESMAN ON YOUR SIDE! Tell him up front he's not gonna make any money on you, this will be an invoice deal. Tell him you'll slip him a $100 after the deal if you get your price. So when he goes up to the "salesdesk", he's fighting for you. When the salesman comes back to you with numbers on the paper, they call it an "a" sheet. Cross it out with a big "X", flip it over right your number on the back, next to it write "T/T out the door", then underline it. The first number you write should be at least $2000k below invoice. His manager will either send someone over or come his self. This is a good sign it shows that you werent talking to a "closer". He might even write a note, asking where r you getting your numbers. If this happends, write "I was thinking the same thing about you numbers".
Typically his second number will be $2000 above invoice. If it is, you write," Split the difference, with T/T, out the door" They usually will jump at it.
What I am telling you is based on 5 years in the business and personal purchases.
Tips:
DONT BE SCARED TO WALK AWAY.
CONFIDENCE IS KEY.
DONT DRIVE THE VEHICLE FROM THE DEALER YOU ARE BUYING FROM.
DONT DISCUSS CREDIT, FINANCE, INTEREST RATE, ETC BEFORE YOU GET INVOICE PRICING.
(THESE ARE BUYING SIGNALS, THEY WILL SMELL IT LIKE BLOOD TO A SHARK)
DONT LISTEN TO YOUR FRIENDS. EVERYBODY CLAIMS THE GOT A GOOD PRICE. MOST DONT KNOW WHAT INVOICE IS.
DONT ANSWER ANY QUESTIONS DURING NEGOTIATING FOR INVOICE.
(YOU MAY GIVE AWAY A BUYING SIGNAL WITHOUT KNOWING)
SHOPPING DURING THE LATTER PART OF THE MONTH CAN WORK TO YOUR ADAVNTAGE.
(DEALERS HAVE A PROJECTED SALES IN UNITS THEY NEED TO MEET, SO DO BANKS. THEY TYPICALLY WILL WORK BETTER DEALS AT THIS TIME TO MAKE THEIR MONTH)
IF YOU SUBMIT YOUR EMAIL ADDRESS TO A DEALERS WEBSITE LET THEM KNOW "NOT TO CALL YOU, NOT TO NEGOTIATE, YOU WILL ONLY ACCEPT INVOICE W/TAX&TAGS, IF THEY DO CALL YOU, YOU WILL NOT DEAL WITH THEIR DEALERSHIP, IF THE EMAIL YOU ANYTHING OTHER THAN INVOICE, YOU WILL NOT DEAL WITH THEIR DEALERSHIP" THIS IS THE MOST EFFECTIVE WAY TO NEGOTIATE, AS OPPOSE TO IN PERSON.
THEY KNOW IF YOU NEGOTIATING THIS WAY YOU ARE A SERIOUS BUYER.
THEY WANT YOU IN THE DEALERSHIP SO THEY PLAT THE "GAME" WITH YOU. ITS SET UP TO WORK AGAINST YOU. LIKE A CASINO THE HOUSE ALWAYS WINS.
MOST DEALERS HAVE THE "NEGOTIATING" TABLES IN THE MIDDLE OF THE DEALERSHIP OR OPEN OFFICES.
(THIS CREATES A "BUYING FRENZY")
IT HELPS TO HAVE YOUR FINANCING ALREADY DONE BEFORE YOU SHOP FOR THE CAR.