Font design is the process of iteratively testing the individual choices that collectively add up to a complete design. You will be testing your font to see if the combination of decisions you have made:
Allows you to read the font
Makes the font feel right to you
Makes the font useful for the the jobs you want the font to be able to do.
As you test the design, you will have to trust your perceptions and design somewhat practically. Much of type design requires that you make letters similar and that you repeat forms.
It is tempting to assume that if you measure the parts and the spaces between the glyphs, then you will get reliable results. While very useful, this approach has real limitations. You should expect to make adjustments if something looks wrong to you. Furthermore, you should feel confident that making changes until it “looks right” is the correct thing to do.
The reason this is true is that there are a number of natural optical illusions that all readers are subject to. These illusions must be accounted for by altering the shapes of letters until they look right to you.
FontForge is libre software that allow to you to design a complete typeface. So you can download, share and install copies without any restrictions on usage – both commercial or personal use is encouraged. It is a community-maintained application, and anyone can contribute to the source code. FontForge is available in easy to install packages for Windows, Mac OS X and GNU+Linux operating systems!FontForge has the same interface on Windows, Mac OS and GNU/Linux operating systems.
Here is a short introduction to the essential features by Dave Crossland at a Crafting Type workshop, a non-profit type design workshop that supports the FontForge project:
For a complete introduction read the online book here [http://designwithfontforge.com/en-US/]