I'm using osx lion 10.7.5 (if that matters). Sometimes, when trying to highlight only half of a word and whatnot I would get really annoyed because the highlighting would automatically jump to the end of the word. I tried googling and never found an answer, until I figured it out myself so here it is,

It should be noted that I'm using a trackpad not a mouse. And I'm using a the three finger drag to highlight.

It turns out when you click right before the first letter of a word, placing the cursor there (if there even is a visible cursor), and then start highlighting from there, it highlights full words at a time.