Well, every dealer is different in their approach on how to do business so there is not an overall secret method that works universally! Most of the things mentioned "can work" but ultimately your best opportunity for the best price is when you catch the dealer at a moment of weakness when they themselves are desperate. The problem is this is completely random and often requires luck. For example... A random Saturday at 5pm when the dealer had forecasted 20 sales that day and had actually sold 4 cars and it's almost closing time. Naturally in a situation like that, dealers will be amazingly aggressive but there is no chart for the consumer to know when and where this will happen consistently. A lot of people will say the last day of the month is good because dealers are chasing a quota and this again can be true but most times that dealer already hit his quota and so it's really just like any other day. I will tell you that another perception is to go on big sale weekends like Memorial Day or 4th of July but in all actuality thats when we made our best grosses because the consumers guard was usually down. A no no for the consumer!
The dealer i worked for here in phoenix was ultra aggressive and I had the license to do basically whatever I needed to do to make sure we did volume... Enough volume that we were consistently #1 in town and in the top ten nationally month after month. For example, let's take a random Tuesday morning at 8am... I get lucky and sell our first car and make a $7000 gross. The next customer is looking at a truck at 9am but won't buy. I drop my price to zero profit... He won't buy. I view this now as a challenge... One I'm going to win so i drop another grand, 2 grand... I finally get him to say yes and I ended up losing $3600 net profit on the deal. Now at 95% of the dealerships out there this would have cost me my job. But the way we justified it was that I had sold 2 cars by 9am and averaged $1700 a piece and was on track for a big day. This is how we chased volume.
At the end of the day, it's mostly luck that will net you that "crazy deal"... Being at the right place in the right time. Your best odds at getting a fair price is to negotiate from an invoice. A reputable dealer will always have no problem showing you it. Many have mentioned joining clubs to get 1% below invoice which is called pp pricing or friends and family but truth be told dont waste your money. It can be had without spending the money. Invoice price is not actual cost for the dealer. The average jeep will net the dealer about a $1500 profit if they sell to you at invoice because they get additional monies from the manufacturer called holdback. The bottom line is if you can walk into a store and pay somewhere between $500-700 below invoice you've made a good deal. Its fair for you and its fair for the dealership. If the dealer wont commit to this then just say "next". Obviously this applies to run of the mill jeeps... Anything that is considered limited edition or limited availability, none of this applies. When the Challenger SRT8's first came out we were making $20,000 profit on each one we sold but thats a story for another day!
Hope this sheds a little light and helps at least one of you, if not more, save a little money!