Perhaps the most important decision in setting an appropriate tone is choosing a typeface or font. A typeface is a family of fonts, each font being a different style (for example, Arial is a typeface, Arial Bold, Arial Narrow and Arial Regular are all fonts of the Arial typeface). There are a number of categories of font including Roman (serif, sans-serif, script and ornamental), Blackletter, Monospaced, Symbol and others in between. Each of these will give a fairly distinct feel to a piece, however as always, it depends on how you use it. Kerning is adjusting the space between individual letters and is often used in detail-oriented projects such as logo design to make the spaces between letters look even.
Using color in design is a class in and of itself, but we can touch upon some general techniques here.