1: Amount of down payment: Avoid leasing deals where you put down a lot of money in down payment. Too much money in down payment could be lost should the car be totaled or stolen shortly after you take it from the dealership. Should that happen, the insurance company will only pay for the value of the car and all the money put down will be lost to the consumer. To avoid this pitfall, make a little or no down payment if possible.
2: Secondly, most cars lose lots of value the moment they are driven off the car lot including leased cars. So if the car is totaled or stolen after you have taken it, the insurance company will not pay enough to cover the actual value of the car, the leaser may wound up paying the balance out of pocket. Therefore, there is exposure without gap insurance. Before sealing the lease deal, make sure there is gap insurance to have you covered in case the inevitable happens.

3: Mileage Limits: Make sure you know your driving habits and demands before you opt for leasing else you could owe lots of money on a car you no longer drive. Most leasing companies put a limit of 10-15k miles, so if you drive a lot more than that you may want a leasing term with a lot more mileage limit.
4: Cost of damage due to wear and tear: when you are leasing a car, make sure you take proper care to avoid excessive damage to the car which you will end up paying for when you return the car. This might cost you thousands of dollars extra money if you are not careful.
5: Maintenance Costs: Leasing for too long a time period may wound up hurting you and will cost you more money in maintenance costs. Shorter term is better, like 3 years or 36,000 miles maximum. Anything more than that may end up hurting your wallet.