Basically, you want to keep different sentences diverse, but phrases within the same sentence should have the same structure. For example, "NWO is drinking a lot of alchol, typed a lot of weird messages, so a lot of people will get pissed off" is incorrectwhereas "NWO drank a lot of alcohol, typed a lot of weird messages, and pissed a lot of people off" is correct. Note that the former was swaps between tenses, whereas the latter has a consistent structure.
Don't worry, you have 2 weeks to get more analyses than me :P