the thread starter wants a direct answer. and this will be helpful to all of us.

and not complaints about the performance and not attacks and reminders about not buying it etc. and not facts about how device is slowing down as you put in more and more applications.

ok I'll give you a direct answer that I know:

-overclock your N900
-install transitioncontrol (faster transitions improves performance)
-install softwares already available that will make your life easier like:
>shortcutd (lets you set camera button to a function eg. call)
>simple brightness app
>quick launch
>call notify
>catorise
>cpufrequi
>headphone daemon
>live focus (improves the performance and functionality of your camera)
>mplayer + SIB (play unplayable video format, really amazing)

I might not have mentioned everything the rest can add up!