I agree with Rednu. However, let me add something to that. I would suggest that you maybe try tempos out for a while. Maybe go with uptempo if you feel like you have the advantage over the other team, if things don't pan out as you expect change to Normal. Unless I am playing a far superior team, or mine is very young, I generally stay away from slowdown, as I like to have the extra posesions. I also feel the same way about Uptempo, unless I am a far superior team or think I can cause extra turnovers or cause more fouls, I stay away from it.
I think that tempo must be experimented with. Don't be shy to change tempos, and see how your team reacts. Then once you find the best tempo only change it to try and exploite another teams weakness or coverup your own flaws.