There are many ways to start a SOLIDWORKS sketch. After starting a sketch, good chance you go straight to the line tool. Why not do both in a single keyboard key with the SOLIDWORKS Line Tool Shortcut.
When you select a face or a plane, press “L” (not capital). This will immediately launch into a sketch and begin with the line tool. Quick, simple, and can save you a bunch of time over the course of a day by not having to click on the Sketch and Line tool icons.