In the 60s Ivan E. Sutherland (MIT) invented and introduced the Sketchpad, the early ancestor of Computer Aided Design (CAD). It featured drafting functionalities like a 2D-CAD system and it was equipped with a touchscreen as output device, a lightpen, tool buttons as input device.
Here is a short demonstration about Sketchpad by Dr. Alan Kay:
Step 1: Basics and which CAD software is the right one for you?
There are several varieties of CAD programs, so which is the right one for you?
Most of the CAD-Software developers offer a demo or trial version, so you can try it. The next question is, what functions you need.
It depends on in which sector you are specialized. For example a mechanical engineer needs a CAD Software, that has the ability to visualize in 3D and simulate the behaviour of mechanical parts. A furniture draftsman requires a CAD Tool with basic functions.
Step 2: My experiences with CAD
Here are few of my project examples:
-)white-colored, huge-wooden letters
Step 3: Conclusion
The most important thing is the realization of your ideas and how to express your imaginations. You begin an idea with prototyping, brainstorming and bring it to paper. Then you continue with the details by using a CAD program.