The first thing you should do when laying out a body of text is to choose your font, its size and its leading. Too many designers rely purely on screen display. Always make many print tests, printed at 100% using the actual layout grid you created to check the overall look, size, leading, legibility and the actual space your text will take. You are then able to make the appropriate adjustments to end up with the correct number of pages you had planned for.
Before you commit to typesetting any real substantial body of text, make sure you have made the right design choices. An experienced designer knows that an 11 point sans serif font will appear much bigger than an 11 point serif font. He will know that Garamond will not be the same size as a Times New Roman, even though they’re both serif.
Notice when you have a flush left text, that it creates a ‘rag text’ on the right side. As a typesetter, it’s your job to make sure that the rag text is nice and balanced without sudden holes or awkward shapes and that you are not creating or using too many hyphens. Actually, you should avoid using hyphens unless it’s necessary to have a professional looking typesetting job. Compare these two columns of text to the ones above and you will have a good example of ‘bad’ rag text and ‘good’ rag text.
Finally, notice how this body of text does not have any ‘widows’ or ‘orphans’, like the text above. A ‘widow’ is a very small line or a single word left alone at the end of a paragraph. An ‘orphan’ is a word or short line at the beginning or end of a column. Widows and orphans create awkward rags and have to be avoided.