How to draw a typeface?
Letterfountain is a good and valuable resource for designers with interest into typography. Available in several languages, the website companion propose a good page about some basics for typeface designs.
Letterfountain.com: From drawing to font
Letter Fountain by Joep Pohlen, Taschen.
Hardcover, 16.8 × 24 cm (6.6 × 9.4 in.), 640 pages, € 49.99