With a new puppy comes training: house training, social manners, recall training, basic command training and of course, leash training. When we are out and about I see all sorts of leashes – most of which are useless for control. I especially do not like the expanding/ retracting leashes and as a survivor of several entanglements at the hands of oblivious dog owners, I have the experience to back that up.
A leash for a new puppy needs to give you the right kind of control so you can correct behavior, make sure the pup does not get into trouble and give you other options as well. While you are socializing your puppy he/ she will be in all sorts of situations so you need a leash that you can use in all sorts of situations as well. Also, remember a puppy will be biting the leash in the beginning and will likely damage it so you want something that will do the job without costing a lot of money.
I recommend a six foot long, one inch wide flat leash that has heavy duty stitching and a clip that is easy to snap on and off of a collar as well as being mounted on a swivel. This is your basic leash and it is perfect for training, walking, stepping on to keep your puppy safely in one place when you need your hands free and looping around your belt to tether a puppy to you.
At least in the beginning, stay away from round leashes, long leashes (over six feet), retracting leashes and so on. They are more of a specialty leash to be used in certain situations. They are also more appropriate for well trained dogs that may be controlled using commands. What you want is versatility in the beginning and a plain old six foot flat leash will do everything you want it to.