Drop Down lists are a common request and question in the Episerver world, for anyone fairly new to the platform. That's because Drop Down lists are a great way to provide users with a straight forward interface for providing a value to a property; the options for values are right in front of them. They also make it easier for a developer working with those property values, because they know what the possible values are that they will be working with. Unfortunately, someone new to the Episerver platform might not know the best way to start creating properties with Drop Down lists.
Linus Ekstrom (http://world.episerver.com/blogs/Linus-Ekstrom/Dates/2013/12/SingleMultiple-selection-in-EPiServer-75/) blogged about the basic approach of using SelectOne and SelectMany with predefined values in 7.5, and Joel Abrahamsson (http://joelabrahamsson.com/enum-properties-with-episerver/) and Anders Nordby (https://andersnordby.wordpress.com/2014/10/16/enum-properties-with-selectone-and-selectmany/), along with several others, have written good blog articles about working with SelectOne and SelectMany properties sourced by Enums.
Aside from linking to those articles to familiarize you with the people (they're pretty cool) and the approaches, this article is to help provide additional methods for building out lists for SelectOne and SelectMany properties you want to use Drop Down lists for.
