I have spent over two months playing with iOS 5. So that helps a little
Go into settings. Then to Notifications.
You will see 3 sections.
1 - Sorting order.
2 - What shows up in the notification center pulldown.
3 - Apps that won't display anything in the notification center pulldown
So lets pick the Calendar app.
The screen that comes up allows you to set all of the features.
Lets set it to on for this demo.
Show items - 5 is good. But you might want more or less.
Alert style. This is a personal preference thing.
I use Alerts for anything I want to get my undivided attention since it pops up in the middle of the screen.
I use Banners for anything that I might want to see but if I miss, I don't care about. But I do set Badge App Icon to on to make sure I see it at a later time.
I use none for apps that only need a badge indicator. For me that would Words with Friends or Hanging with Friends.
Badge App Icon is the little red number counter.
View in lock screen is for when you just turn the phone on and want a quick glance at items that haven't been looked at directly.
Hopefully that helps.