I love text in my books. I'm never satisfied with my altered books if they don't have some quotes, or words. But how to apply them? There are many ways. Rubber stamp letters. Stickers, Rub ons, handwritten or printed, printing with your computer and printer (good for playing around with sizes and fonts), collage with cut out words or letters, stencils, purchased sheets of letters, or - the most fascinating - found words.
Find words on the page, then block out the other text and just let those words show through. This is such a fun way to alter a book. I use it at least once in each book. Some artists do entire books in this way and don't add images or other art work. You really should have the experience of trying it. The site for the absolute king of found words is: http://www.tomphillips.co.uk/humument Do take some time and look at what he has done.
I'm sure you can think of other techniques I've missed. I have cut out poems from books, or jokes from magazines to use. I'll post some pics later of some different methods of adding text.