Also a cool trick to keep in mind, when you work with extrude sometimes you forget to extrude or undo steps to an extrude step that you have made, and that lead to errors and double edges.

To check your edges from time to time, select your object, right click on object and chose vertex face, in vertex face mode you will be able to see your model fragmented into faces that way you can search for edges floating around your model, if u see edges that are not connected to model faces, select floating edges and hit CTRL+DEL.