Not passive? Take initiative; not tentative; be decisive. More attacking; create your own lucks. Active and fast games. Not screaming/shouting disrespectfully at your opponent or judges.
To be aggressive you have to be fast on your feet. Always work hard to get in the best possible position to play a shot.
Yes. There are many ways, even i don't know much about this. Do Plyometrics or the p90x3 exercise, and many more. but it must be geared towards badminton I think you should concentrate more on the defending side. If you are in a position to defend, you should concentrate on how the shots you produce can make you be the attacking side again.