1) end of the month is the best time to get a deal. The closer to the end of the month, the better the deal. However, if a dealership has already reached their quota or sales goal a few days early, you arent getting a great deal if you walk in the last day or two of the month. I say you go in with about 5-7 days left in the month and try and see how the negotiations go.
2) The later you get into the year, usually the better the rebates, meaning the better the deals...... However, It all comes down to the economy, gas prices, how well or bad the quantity of vehicles the manufacturer is moving each month and other macro economic things. Last report i heard, was auto sales were a little soft last month as a whole. Gas prices have bottomed, but they are rising and spiked last week. I'm hoping that the dealership i am working with is going to be in a tough spot and really offer me a great deal on the truck i started shopping for two days ago..... i'm about 90% of the way towards the deal i want......and i got time......they dont, the month ends is 6 days