The Letter, Text, and the Grid

What are the advantages of having a multiple column grid? 

Multicolumn grids are more flexible than a single-column grid, and become more and more flexible with each column. This flexibility can help the designer to articulate the hierarchy of each element in a publication by creating different zones for different things. Text and images can span a single column or they can spread out through multiple, and not every inch of space has to be occupied. 

How many characters is optimal for line length? Words per line?

45-75 characters is optimal for line length, or about 12 words per line.
Why is the baseline grid used in design?

Baseline grids serve to anchor the layout elements and create a common rhythm. 

What are reasons to set type justified? ragged (unjustified)?

Justified text creates a clean shape on the page and uses the space efficiently, but sometimes ugly gaps can occur within the lines, so designers have to be careful to use a line length that is long enough in relation to the size of the type. Ragged text (unjustified text), respects the organic flow of language and avoids the uneven spaces that can sometimes happen when using justified text.
What is a typographic river?

In typography, rivers of white, are gaps in typesetting, which appear to run through a paragraph of text, due to a coincidental alignment of spaces.

What does clothesline, hang-line, or flow line mean?

A "hang-line" is a line that divides the page horizontally and becomes a place for body text to "hang" from. Elements within the publication will gravitate towards this line and provide internal structure for the page.  

What does type color/texture mean?

Type color/texture refers to the space between letters, words, and lines of text as well as the weight of the font. Typographic color can be used to control the hierarchy of the text.
How does x-height effect type color?

Typefaces with larger x-heights (such as verdana) help reduce type color and make by making large bodies of text less dense and therefore easier to read. 
What are some ways to indicate a new paragraph? Are there any rules?

Using an indent accompanied by a line length has become the standard for indicating a new paragraph, but designers have come up with some other alternatives, which include:

• paragraph spacing
• outdent and line break
• extra space inside line, without line break
• symbol, without indent or line break

One rule that designers follow when indicating a new paragraph is to make sure not to combine too many signals. Using paragraph spacing and indents together, for example, gives the text block an indefinite and unpleasant shape.