Proper length is based on your height, wrist to floor length and putting posture, i.e. do you crouch over like Jack Nicklaus or stand taller like Tiger Woods.
The standard lie angle for putters is 70 degrees. A too upright putter will cause the ball to go left of your of your target - a too flat putter will cause the ball to go right of your target.
Putters on average have 3 degrees loft. Depending upon the amount of negative or positive shaft lean you have at impact your putter may need more or less loft to create a proper roll.
The iPing Putting App is an excellent tool in determining the right specifications for your putter. I use it in all my putter fittings. Call the shop to schedule an appointment and learn how a custom fit putter can save you strokes on the green.