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Because InDesign is primarily a layout and design tool, most type will originate in other programs such as Microsoft Word or InCopy, the companion program to InDesign. Just like graphics, all text will source an original file via links. For the ins and outs of placing text from work documents and specialized formats, please look to the video below from Adobe TV:
Size, Leading, Kerning and the Options Bar
Character size is measured on a point scale. The common 12 point font is equivalent to 1/6 of an inch. This Most people have had to double-space an essay. Leading in refined method of line spacing rooted in the printing press. Printers would add strips of lead above the characters to create space between the line. To this day, leading relates to the space above the line highlighted rather than the one below it. These concepts were both covered in the original starting video but can be reviewed in writing on Adobe's help pages.
Kerning is the process of manipulating the area between two specific characters. This can be manipulated through the Options bar on the type tool (described in the video below) as well as its close relation, Tracking.
The eyedropper tool can be a timesaving fix to manually change type to match a style. For an introduction to the Character and Paragraph styles panels and an overview check out this link from Adobe's help forums.
Unlike other presentation tools such as Powerpoint, text that is too large or lengthy to fit in a text box is hidden and stored in the memory of the computer. This action, known as overset text, is signified only by a red plus mark in the bottom right-hand corner of the text box. It is important to understand that this text does not purely "disappear" but rather InDesign anticipates your actions by preparing it to be put in another text box. A brief visual example is included below:
Maneuvering through text
Selecting and changing type on a page can be complex especially when there are multiple text frames linked together. For some handy tricks and tips, look to the video below, also from Adobe TV.
At some point, everyone runs into a circumstance where a text box and a graphical element intersect, overlap or interact. Here is a great video breaking down how to deal with this interaction using the text wrap panel.
Paragraph and Character Panel
Both the Paragraph and Character Panels allow for a significant increase in the ability to add and manipulate the styles on multiple instances of type. They provide much more control and depth than available directly in the options bar.
Paragraph Panel Overview
Character Panel Overview
For higher level type tricks and tips, check out this article by Jo Gulliver from Creative Blog.