Yep, rep tempo. First make sure you do the exercise with correct form, second step is so make sure you focus on your rep portions, the positive, negative and if you want to (which I recommend) the static. Next step is to master what tempo suites your training so here is it.
The first number is the positive portion of the rep in seconds
The second number is the number of seconds for the static
The third is the time in seconds for the negative
The final number is the number of seconds for a complete stretch
Example: 2-3-1-4 would be a 2 second positive, 3 second static hold, 1 second negative and a 4 second total stretch.

Hypertrophy
Time under tension is what this is all about. Here's  my recommendation
1-1-3-1
1 second strong positive, 1 second static hold, 3 second negative and a 1 second total stretch without locking out. Make sure you don't lock out because you'll loose the tension, even when your muscle is stretching, it is under contraction, just not during lockout because your joints take the strain off your muscles

Strength
My recommendation:
1-0-2-2

1 second or as fast as possible powerful positive, no static hold (you don't want to tire yourself out, it's about the heavy weight, not fatiguing the muscle from extended duration exercise), 2 second negative (not too slow but don't drop the weight, in powerlifting in competitions you have to show you can control the weight) and a 2 second stretch. The stretch on this one i like to lock out on for deadlifts, squat and bench. It let's me feel the weight while not being under tension, it let's you collect yourself for a second or 2 while preparing for the next rep. Plus it's always totally badass to stand in the gym holding a 210 kilo bar casually while the people be mirin' brah!

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Power
This is an area I haven't trained as much so my advice might not be as valuable but if I ever do power i do this tempo:

1-0-1-2
This way, your positive is powerful, you have no static hold to tire the muscle out (power is about being explosive not time under tension), a 1 second positive so you're not letting the weight go but are controlling it down doe a 1 second count then a 2 second stretch. The stretch is important! The stretch, stretches out the muscle and negates the spring effect. Your muscles are like springs and coils, when you come down from a rep it was to snap back to contraction, it helps with lifting heavy weight. This is like when you see someone bounce at the bottom of a squat, it's the same principle. Having a long stretch stops this and forces your muscle to reply on it's own explosive power to complete the rep as apposed to its elastic properties. It makes your muscle work much harder to complete the rep, increasing power and strength. Pause at the bottom of a squat for 2 seconds with a weight you do with no pause, you won't that's the point!

 

Speed

Speed reps are simple. As fast as you can! Just bang them out as fast as humanly possible without using terrible form. Usually working to your speed threshhold (the weight where you start slowing down) with low reps brah!
 

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Fitness

Fast reps for days son!
tempo is obviously as fast as you can go with good correct form. Burpees, squat jumps, box jumps, sprints and all other fitness exercises, need that fast non stop tempo to make you fit and machine like. No pauses no static holds, go all out!

Calisthenics

I love calisthenics with a passion! I have done enough of it to know what works and here is what I have found to be the best.

1-1-1-0

This is for prety much all exercises except isometrics (static holds)
This means do a quick positive, come straight back down and pause at the bottom for a second. This is to kill the elastic response in the muscle to make you use your strength instead of physics to complete more reps.
HOWEVER, if you are going for calisthenics and you're doing endurance training like a death set then the tempo you use is a simple:

1-0-1-0
This means a quick positive, no rest, quick negative and right back up. Strict perfect form on most of your reps is a must!