These pedals have been around for decades and really deserve their place in any setup. Everything here is straightforward - input/output (jack) and three knobs adjusting volume, gain and tone. You can power it with a 9V battery or use a power supply. An LED is light when the effect is turned on. I have to say that they could have started buidling a more modern LED into this effect by now as they are really quite difficult to see at times.
This unit was built to last and the switch looks like it can take a beating-and-a-half and brush it off like nothing happened.
Well the setup is basically like on any amp. I don't think you will really need a manual. Volume dials in...well the volume. Tone and Gain do the same. Just make sure you adjust the distorted sound to the clean sound. A lot of guitar players don't do this correctly and instead of gaining more intensity in their sound they tend to 'drop out' of the mix.
I believe the biggest misconception with this pedal is that it does not primarily get used to create a distortion sound. It is supposed to overload the preamp slightly to saturate the tubes - resulting in a distorted sound. But really if you want a full blown distortion for hard rock or the likes then you will have to use another pedal (or one in conjunction with this one). The Tubescreamer is more supposed to 'rough up' your signal and add a warm, slightly edgy but still very clean sounding saturation that allows you to dial it out with your volume knob. You should still be able to play that F#b9#13 without having it being washed out.
For some this pedal is a bit too warm - maybe go and try the Alberta then from T-Rex. It costs more but seriously delivers. I use the Screamer with a Bluesdriver (in that order) and in combination I get a very creamy sound with a lot of sustain. By themselves they give me 'crunch' and 'a bit more rocky crunch'.
I really love this thing. Some people can't stand it but for them Boss built the Metal Zone. It adds just that bit of punch and dirt I need at times and I can handle it very well with the volume knob on my guitar. If you plan to do this try to turn the Tubescreamer up a bit so when you dial back you won't get lost in the mix. It is always good to have a bit of volume reserve anyway - but please let the sound engineer in on your little volume tricks!