Every profession has a set of rules to be followed, to ensure the best results are stained. As a designer using typography, one must keep these rules in mind:
Never go overboard with the fonts. If you are working on a single page or a document, limit to two or three fonts. You can highlight, bold or underline it, to get more attention. By using a different font, you are not only cluttering the page but are also confusing the reader as they would not know which part of the text needs more attention or is more important.
Choose a font that is tried and tested. Always have trial runs for a new font, print it in the form the customer wants and see for yourself, how it looks. This is important because many fonts look appealing on screen but when printed, they may look cluttered or not readable. You don’t want to give your client something they can’t read.
Select the right size. Different type faces are created in different sizes. While some are fat, some can be too thin. Hence using a standard size 12 will not suffice when you are using different font. The size has to be decided based on the readability of the font.