We have touched on this topic before, but it is one that we should revisit. Most of the time their, there, they're or lie, lay or accept, except do not change the meaning for the reader. It is intersting how our brain makes that correct interpretation. Still, MTs should be masters of the language.
There is a very nicely written page on several commonly misused words at http://wsuonline.weber.edu/wrh/words.htm Take the time to go read it now.