If you do not want to employ a professional draftsman to design and diagram your inventions, then I suggest that you either read a book on the subject or get a good patent drafting software program to help you. A professional draftsman will be much more costly and will not have the detailed knowledge about your invention that you do.
The best book that I have found on the subject is How to Make Patent Drawings Yourself: Prepare Formal Drawings Required by the U.S. Patent Office. What I have found beneficial about this book is that it is easy to read, whilst providing information on the strict rules of the U.S. Patent Office and how to easily comply with them. It also saves you quite a lot of money on the drafting process. A great spin-off of being able to do formal drawings, something this book teaches quite well, is that it allows you to visualize your invention as a whole yet also in individual segments. This means that if you have the general look of the invention mastered, you can tweak the segments to make your invention more efficient or productive.
For a more general book on drawing, that will help you develop your creativity as well as your technical ability, I recommend, The New Drawing on the Right Side of the Brain by Betty Edwards. I have found that this book’s author is one of the few people who truly know how and why we draw the way we do. It is all in the mind, not necessarily in the genes. In building our drawing skills, Edwards actually helps us build our creative faculties, as all mental skills are related in some way or another. Check it out.
There are two software products that I recommend, depending on your technical skill level (many inventors don’t have any technical skills, so don’t worry!).
For the not-so-technically-skilled
If you are not technically skilled, then I recommend either Microsoft Visio Professional 2003 (the more expensive version) or Microsoft Visio 2003 Standard. The reason that I like this product is because of Microsoft’s “SmartShapes” technology, which completely simplifies the drawing process. All you have to basically do is drag the many pre-defined SmartShapes onto the desired location on a page and then edit them to suit your needs. You do not have to be an artist or computer wizard to be able to come up with some really professional-looking diagrams for your inventions. Its often a good idea to sketch out your invention first on paper and then recreate it on your computer with Visio.
For the technically-skilled
I recommend that you use AutoCAD LT 2004. This program is the standard in the technical design industry. It combines drafting and collaboration tools that allow you to create 2-dimentional designs and diagrams. If you have many inventions or want to become a serious inventor, I suggest that you invest in this product. Once you get the hang of the program, you will be able to accurately design prototypes for the manufacturing process. The great thing about AutoCAD is that it allows you to literally design your products to the inch. You can then securely send the design file to the manufacturers who will take it from there.