The first step is to simply prepay for many supplies and goods that you use to produce your product or service. This serves two primary purposes. It will help minimize your expenses right out of the gate for a very uncertain 2013 and if done properly will give you a quantity discount when placing a higher volume order. Plus, most vendors raise their prices for the subsequent year. So you are saving money in three different ways: Quantity discounts, avoiding raised prices and taxes. Note: Make sure that you don't forget in January that these costs were paid for in December or you might develop a false sense of security when you consider your January P & L.
Most government situations will allow you to pay more in taxes now to credit your account for the next tax period. If this is not the case, a simple, yet justifiable, error in the government's favor will not raise any red flags. Just be careful that your state doesn't require you to amend end-of-the-year returns or this will not do you any good.
If you make any quarterly commission or bonus payments based on a previous quarter's performance, paying at least a portion of these out in December instead of January will happily cut into your net profit. If you want to avoid scrutiny, categorize these as "holiday bonuses" and deduct the amount paid from any quarterly bonuses usually paid in January. If the bonuses pertain to work performed in 2012, this is perfectly legal and will simply look like a nice gesture by you to give your commissioned employees more money to buy gifts for the holidays.
There is such a delay in shipping items in December that many orders do not arrive at their destinations until well into January. It is easy and allows some of your better clients to pay for orders in January versus prepayments. If you sell things on the Internet, it is easy to a run these sales through on payment "posting" dates as opposed to the actual date of a sale.
Also consider deferring payments by simply holding deposits and logging/recording the deposits in January, particularly if you are on a cash-based versus accrual-based system.
NOTE: Now is not the time to pay for things your business can not afford and paying extra taxes will do very little to keep your business in healthy shape for 2013. Your future growth is what will eventually provide that extra revenue the government seeks.