Use of Fonts
I have a relatively conservative approach to the use of fonts. This may partly be based on the fact that when I grew up in the computer field, there were relatively few to choose from. I like to think, however, that functionality is at the basis of my position – that text should be readable and attractive.
Today, there are huge numbers of fonts ranging from simple ones to extremely complex and ornamental ones. In addition to the variety, you can do a lot with them, such as change their size, embolden them, or italicize them. You can make them different colors, and so on.
Some people are tempted by all the options and want to incorporate as many of them as possible. This is a mistake because the reader's eye will be overwhelmed by what it sees and reading will slow down and comprehension may suffer. I suggest that you look at printed materials as well as text on the Web to find pages or screens that appeal to you. Analyze them to try and determine why they are appealing. Then try to replicate what they have in your own work.
My own approach is to standardize on a set of styles to which I adhere throughout the product I am developing. This necessitates making these style decisions before you start the development process. You may decide, for example to have four levels of heading and one level of text. Or you may only have two headings and two different text styles. Whatever decision you make should be based on the material you are working with. Be prepared, however, to find that some aspect of the product does not fit the material even after you have made the style decisions. Products have a habit of surprising the designers and developers.
My general bias is to use what are called sans-serif fonts, such as Arial or Helvetica, in differing sizes for headings and serif font, such as Times Roman for the body of the text. I find the visual differentiation subtle but effective. Furthermore, it conforms to general research findings that serif fond is easier for the eye to read when there is a quantity of text. Try this combination out and see for yourself.