I need advice on how to haggle with a car dealer. I am looking to buy a new car and I would like some hints/pointers on how to get the best deal possible. Please help!

The ability to get a bargain depends on how desirable a given car make and model is, but there are some general rules.
Say you are looking at a few brands but don't say what or where.
Most American brands have a leeway of about 3% under the INVOICE price not counting $500 dealer destination charge, foreign brands 1% to 3%, with many at 2%. Dealers like to tell you you are getting it for $1 above invoice, but that's all finagling. Invoice on a 20K car might be 18K, and then you can haggle down as much as another 600. Maybe.
Don't get sucked into double talk dealer costs. Just decide on an amount and stay with it.
Don't take the salesperson's card, write your name and number on it and give it back. If they pester you, just say you bought a car, bye.
Don't wait in the showroom while they 'talk to the sales manager.' Say you need to visit other dealers.
Don't get sucked in by extras. Tons of profit in them.
Bring a notebook with you and write down info to make you look serious about the purchase.
Know how you will pay for it. Say you have financing all set at your bank, unless they are having a promotion. Be careful about promotions and what you really get for those low rates.
Be prepared for being quizzed and ignoring the questions. That's all designed to throw you off and appear to have the upper hand, to decide for you what you want. YOU know what you want.

So much depends on where you are at, do you have the money in your checking account to write a check for the car ?

Do you have a loan already approved at your bank or credit union where you can still just write a check basically.

IS it a new car or used car. Buying one off the lot or do you have a special car in mind that will have to be ordered ?

If new will you take a strange color or type that has perhaps been on the lot for a while.

I normally walk out of the office of the dealer at least twice, never talk to the salesman, I don't sit and wait while he goes and pretends to talk to someone else. I explain that if they want to sell me a car , get everyone needed to make the deal in that room now, or I walk, and I have walked several times. If I do walk, I always drive by and show them my new car when I buy it somewhere else. *** to prove a point.

I go at the end of the month when they are more worried about making their quota or commission.

I don't mind taking my time, if I get a offer, it has to be in writing and I may take it to a dealer of the same brand down the road and say "beat it"

Get the Consumer Reports guide. If you are a subscriber, you can get a report showing the approximate dealer cost of the vehicle, so you have an idea of the dealer's wriggle room.

'Invoice' or 'dealer cost' include the extra 2-3% I mentioned, which is called holdback. The manufacturer charges the dealer for it and then gives it back, quarterly. It may or may not be part of the amount you can get taken off.

I agree about walking out and waiting for them to chase you. That's why you give them your phone number. And it gives you time to go look elsewhere and then go home and think, compare, and research.