In this tutorial you will learn how to create a fluorescent lightbulb. We will work a lot with spline vertices and we'll do some box-modeling as well.
In the Top View create a Helix shape preferably starting right in the center of the grid. Go to the Modify panel and set its parameters as follows - Radius 1: 30, Radius 2: 30, Height: 80, Turns: 2.75, CCW rotation.
Press A on the keyboard to activate the Angle Snap, then - in the Top Viewport - Shift+Rotate the helix 180 degrees to clone it. Choose Instance and hit OK.