I'll repeat the advice to start "flat", for whatever that means on your rig. When you get some time to play around, try adjusting all of your EQ controls away from flat, 1 control at a time, both + & - to get a sense of what effect you can detect from each of them. Be a little conservative as far as how much you change anything - give it just enough change that you can tell it's changed. Once you've got a handle on what each range does by itself, try combinations.
"Scooping" refers to setting a graphic EQ (typically) so that from a distance, the whole thing looks like a smile, with deep cuts in the middle, no cut or even boost at both ends. While this may legitimately be the best way to get the sound you want out of your rig, the problem is that often people try to EQ by eye rather than by ear & set according to the numbers instead of what they are hearing. You don't use your ears to feel, your eyes to taste, or your tongue to see, so why should you use your eyes to decide how to manipulate sound? Trust your ears.
Conventional wisdom is that you should avoid boosting. If you want to boost a frequency range, cut the others instead. The reason for this is that whatever you boost comes out of your headroom - the difference in level between your average sound level and the point where something clips. Bass can be a very percussive instrument, with sudden spikes in amplitude. For example, you may have 12 dB of headroom. If you have occasional spikes up to 9 dB above average, & you boost an EQ range by 6 dB, when you hit one of those spikes in that particular range, your signal is going to be 15 dB above your average signal. That last 3 dB above the 12 dB of headroom is going to be "clipped" off the top of the waveform, distorting it. That may actually be an effect that you want, but within limits - you don't want to let anything clip for very long or some piece of gear is not going to appreciate it.
You may find yourself liking certain EQ settings & use them often. If you do this, it's a good idea every now & then to restart from flat & try again. This can help you make sure that you've got what you really want, or you may discover a tone you like better.
As others have noted, what sounds great to you on the stage, just a few feet from your amp, may be completely different out in the audience. As well, every room is different & even the same room can sound different on different days, different full vs. empty, etc. Recognize that more often than not, the stage is about the worst place to tell what anything sounds like out in the house. FOH engineer doesn't set your monitors according to what sounds good to him, out where he sits! Likewise, expect that what's going on out front is not the same as what you're hearing on stage. It may be better or it may be worse, or both in different ways, but you can be very sure that it's different.
What I do when I set up is EQ so that I can hear every note - every string on every fret. Again, starting flat, I'll play 'em all partly as a warmup, but also to be sure first that I can hear every note, & also to fix any note that may not sound right.
They're just reasonably descriptive mnemonics for the way I hear things.
Scooping mids is just fine if it makes the music you're playing work. I tend to have my tone slightly scooped as well. There's a fine line between having enough mids and making your amp sound like it's made out of cardboard 
