I previously shared a tip on how to launch the Mac Quick Look application with a three finger tap. No question Quick Look is your friend when you need to a glimpse into a file without the overhead to launch the application associated with the file type.
Unfortunately, if you double-tap to attempt to select a word or click and drag to select text, you will open the document or move the Quick Look window on screen, respectively.
Good news is you can change this default behavior. Below is a screenshot that shows Quick Look and a block of selected text:
To update Quick Look to allow for text selection, from a terminal enter the following:
defaults write com.apple.finder QLEnableTextSelection -bool true