Very basic compression level question?

Yes, it's been discussed many times, but this basic concept still troubles me. I've got a kick - sounds lovely. I just wish to compress it a bit. The track level (pre fader metering) is at -2, which I believe is fine (correct me if I'm wrong please).  The post fader track level I bring to -6.  Now, I throw a compressor on the kick track, which brings my post fader level to -4.4.  If I am correct, I want to bring it back to -6 so I can compare equal levels with and without comp, and not get suckered into thinking with comp is better because it is louder. How do I adjust the compressor - input level, makeup gain, or output level? I can get the level back to -6 by adjusting any of these three, but which one SHOULD I be adjusting?  

Makeup Gain.

Thanks for the reply. When/how exactly should I be using the input and output on the comp? Or perhaps the better question, what levels should I be looking to have at both the input and output stages, after makeup has been applied?

I wouldn't worry so much about the input and output.

Use your ears. See what lowering the threshold and increasing the ratio does to the original sound.

Look at the gain reduction on the meters. There's no golden rule except using your ears.

Avoid using Auto Gain.

Much appreciated. Just to clarify then, the only thing I need to do to make sure I'm comparing apples to apples (compressed vs non-compressed) is make sure the output levels for the track match? And to check that, do I look at the stereo output level (mix bus minus any plugs) without compressor, add compressor, refresh the output level indicator, and adjust makeup until it matches the level I had without compressor? 

To match levels, bypass the plugin and adjust the makeup gain when engaging the compressor again.

If I am correct, I want to bring it back to -6 so I can compare equal levels with and without comp

Not exactly, because the two signals you're comparing have a different dynamic range, a different crest factor etc... which makes it impossible to be equal in levels at all times. If you match the peak levels as you suggest, then the compressed signal will sound louder than the uncompressed, making it nearly always appear like it sounds better. Therefor the best way to compare your compressed and uncompressed signal is to match their level by ear, not by number. And that level matching may be different in different sections of the song.

Ah, that makes absolute sense - thanks David! And you as well, triplets! I'm always so grateful for this forum.