The most commonly used style of saber is the single blade. The length of Hilt, Blade, or color, is the preference of the user.
To start, you should explore sabers on the commercial market. Two of the fans favorites in balance and durability are from the manufacturers SaberForge and UltraSabers. Other more common but less resilient models are the Obi-Wan Kenobi and Darth Maul Force-FX Sabers from Master Replicas and Hasbro; one is a single hilt length, while the Maul is double, or staff length. When you decide on a hilt style, you will then find the blade length. Double hilt staffs are discussed in our Hilt Variants page.
Average Hilts size will range around the length of a users Wrist to Elbow ratio. Single handed blades will naturally reduce in size. Again this depends on the comfort of the saberist.
See how Michio Kaku describes making Lightsabers. Is he correct?