Here's a thought, which is dangerous, but who are we if not those who laugh at danger?

Sit down with your players and say "this campaign will start 2 months after the events of Independence Day. What kind of characters would you want to play?"
Then let them brainstorm their characters aloud all through a game session. That's the whole session--coming up with a character idea. And *you* take notes through the whole thing. When somebody wonders aloud "hunh, what if there was a military coup in the US?" you as the GM-to-be can (and should) point out that the POTUS is in fact alive, and a war hero at the end of the film, and the patriotic groundswell is likely to be at VJ-day levels. If they then concoct a reason that there's a coup anyway, and it's a least plausible (see MilitiaJim's Aztlan notions), go with it. Then let the conversation continue, madly creating your background and first half-dozen adventure seeds from what your players are throwing around.
Now you may have a play group that's not ideal for this, and if so that's fine--don't do it.

But I've sat with a number of groups that could pretty much write your world for you if you gave 'em time. I myself can't play in even a one-shot game without creating a page and a half of backstory for my character that fills in little flavorful corners of the campaign world for my own use. It's a sickness. Of course, if your players have my sickness, then tap their eeevil little minds and see what kinds of crazy you can all come up with together.
I have already picked two of the players minds a bit but getting the entire group there might be a good idea. though i likely won't be adding zombies or the like.
I am looking to have pretty good players I play in a shadowrun game one of them is running going onto 4 years. One has played in a previous Spycraft game I ran <<a very roger moore campy bond setting>> then I will get one or 2 random people to round out the group.
Dose any one have any suggestions on Tags?
How should i handle alien science just add another section to the list of focuses?