Com, these look right! I tend to look at the parts of speech to remember which one to use. For example, "passed" is from the verb "pass" --Right now, I am passing him in the hallway. Yesterday, I passed him in the hallway.
In the second sentence, "walk" is the verb and "past him" is a descriptive phrase telling you where he walked. So, I try to remember that "past" is never a verb (like in "the Ghost of Christmas Past").
I can totally see where this type of thinking would break your concentration. In fact, it's one of the reasons I have so much trouble writing and have a much easier time editing! But, hey, isn't that what an editor's for?
BTW, Com, I just finished GFD and SM and you totally have me at the edge of my seat! Your grammar is fine, but lots of times you have letters missing from words --not spelling mistakes, but like missed keystrokes. A few times, I had to stop and figure out what word you meant, but otherwise it usually doesn't bother me. From you A/N, I take it that you won't be updating those any time soon?