<- O.P.
Ah, thank you very much Clive. Your answer does clear things up somewhat. With that new light shed on the subject, I think the other problems I was having are less grammatical errors, and more just an issue with my naive logic attacking my... questionable skill with English grammar. Hehe.
In case you are interested, one of the other problems I was having: Lets say I substituted "Now" for "This" or "Then" for "That" in the original sample; thus, "Now it was Brenda's turn to laugh," and "Then it was Brenda's turn to laugh." Using "Now" with "was" throws up red flags for me, but I think I understand now that its not necessarily a grammatical error, just my misunderstanding.
I really appreciate your help on this matter and everyone's help in general. I have spent a few hours now just browsing through others' questions and answers. This really is an amazing resource. I have learned so much already. Hopefully at some point I can contribute something too. Thanks again.
P.S. Do you happen to know, when writing in English (fiction), is it acceptable to bounce between tenses for different sentences? paragraphs? chapters?