A high and low shelf should get rid of a lot of the extra 'noise' produced by a guitar amp which you don't need in a mix. So now, if you don't like the sound you just recorded, you know that there are a number of physical parameters you can change which could affect the EQ of your guitar tone.
First of all, if it sounds too tinny (adjectives to describe EQ are always slightly controversial, but by tinny, I mean too much of a prominence in frequencies from 2kHz up), try reeling off some of the treble, or high mids on your amp, or alternatively, try switching pickup on your guitar.
If it sounds muddy, and lacks clarity, you need to cut some of the low mids or the bass frequencies, and perhaps you should consider switching to your bridge pickup.
The fundamental job of EQing a guitar involves identifying nasty frequencies and CUTTING them, when you get more to grips with it, then you can start boosting, but for now, try and find the frequency you don't like, and get rid of it by using the EQ on the amp (or the POD HD etc). You'll usually find it will be the mid control, or the treble control (we'll get onto cutting frequencies on an EQ plug-in or rack-mounted unit later in this article).
Then, record the part again, compare it to the previous take, and see how it sits in the mix. Remember, even if it sounds awful in the room, but sounds great on your DAW, then that is absolutely fine, it doesn't matter how it sounds in the room.
If you absolutely cannot get rid of those nasty frequencies, then you need to start playing around with microphone placement (literally just change the positioning by very small movements until you find a sweet spot, a few millimetres to the left or right can make a huge difference) or even the physical position of the amp within a room. If your amp is in the corner of a small room, it might sound a bit boomy.
In the middle a large room with lots of natural reverb, then it might start to sound a bit glassy.
You should be able to get a great guitar sound, just by experimenting like this (in a logical and pragmatic way) with EQ and compression.
Armed with a half decent amp, an SM57, and a DAW, then there is absolutely no reason you can't get a great guitar sound.
Just record, listen, adjust, and re-record. Repeat this process!
If you've tried all of the above, and you've put the time into changing the EQ settings or mic positioning, and then testing it in the mix, and you still have some nasty frequencies you want to get rid of, then you need to carry on reading.
In just a minute, we'll look at frequency notching, and advance use of EQ software. We'll turn you into a frequency expert.
But if you take away one thing from what you have read so far, then just consider that the guitar is a collection of individual frequencies, some of which are more pronounced than others, some of which sound (subjectively) 'better', some of which sound 'worse'.
When you have recorded your guitar, it can be manipulated so much further. Once you master EQ, you will know 'tone' inside out, tone is a complex menage of different frequencies, and getting the right blend of frequencies is the key to great recorded tone. EQ is king, and you need to persevere with it.