Generally it's done through your work, since above $50-$60k mark, the tax breaks make it relatively cheap (i.e. only costs you 50% what it would otherwise - the rest is tax dollars you would have lost anyway). Usually you will need to be a certain level within the company before they let you as well.
Lease companies quite often have good dealer relations, and can get $5k or so off the list price of a vehicle . . .
The car doesn't have to be new (I think), but I think its much harder to get a lease on a second hand car.
All in all, its only the tax breaks that really make leasing worthwhile. Otherwise, its fairly much an expensive loan, and you don't end up owning the car at the end anyway (unless you payout the balloon payment at the end - probably 20% of the inital value of the car). Talk to your employer about it more (probably HR or Finance Dept's ).
Try a search on it here - there were some posts last year about leasing (some way of doing it very cheaply).
Try looking at some of the novated lease sites. I have a novated lease through SMB Novalease they have good site with Calculators so you can have an idea if it might benefit you. You really need to be doing more than 25000 km /year for it to work for because the level of fringe benefits you pay relate back to the amount of km you do. With SMB you can have a secondhand vehicle just has to be redbook valued at more than $15000.00. It works well for me you really have to check with your accountant or somebody in the know to see if it will benefit your own situation.
A novated lease creates a tax deduction for a car & expenses for people who dont have business use. If you do have business use, then l find borrowing the money (against the house) gives me a loan at house interest rates and the added flexibility of not being tied to leases etc. it works better for us and works out cheaper for me as we have 75% business use.
Having said that there are other considerations depending on your financial situation. Novated leasing can significantly reduce your taxable income and so bring your income into a lower marginal rate. if you have negativley geared investments then this will obviously reduce what you get back. Novated leasing can also reduce your income in the eyes of the banks depending on their lending model, and so reduce servicability if you are going for further loans for home or investmanet propertys. Obviously both of these outcomes reduce the appeal of leasing significantly to some.
So there is more to consider than just what is cheapest, you also need to take into account how leasing will affect whatever else you may have on the go now, and into the forseeable future.