Not just anything can be cut onto vinyl. This isn't a digital format where anything goes, there are limitations - some of these limitations are what makes vinyl such a special medium, some of these limitations are a pain in the neck. This section is here to try and limit the amount of neck pain for everyone involved.
I've tried to state everything as simply as possible so as you don't need to be a high flying technical wizard to know what I'm talking about. Some of the stuff here is vital to know... some of it just interesting, but some of it is vital to know.
More Is Less
The more sound you have on a disc, the less room there is for groove space. The less room there is for groove space, the quieter the record becomes. The quieter the record becomes, the more you need to turn the volume up, and the more the background noise becomes apparent, and the lower the quality of the listening experience becomes.
The sounds you hear when playing a vinyl record are formed by the lumps and bumps created when a record is cut. These lumps and bumps cause the needle to move around, and the groove needs space to allow for this movement. If you pack too much onto a disc, the groove needs to be thinner, the needle can't move around so much, and the sound is affected.
Bass uses more groove space than treble.
So for optimum cutting levels, please see the guide below. Note that this is a guide - quieter recording can fit more on, louder recording can fit less on, but this is a general guide.
Outside Groove vs Inside Groove
The outside of a disc spins faster than the inside of a disc. This means the quality on the outside of a disc is better. Which means if you are getting a disc cut which has more than one track per side, then the first track you put on each side of the disc will have the best audio quality.
Some people may want to use this knowledge to put their quieter tracks on first to give them the maximum possible volume level, some people may want to put their loudest most banging tracks on first to utilise groove space. The choice is yours, but it's a useful tip to know.
Treble And High End
Too much high end will not work. Too much treble will cause uncuttable distortion. Use a de-esser to reduce sibilance. Counter high pass filtering with low pass filtering. Levels possible for digital distortion are not possible for analogue distortion.
Remove everything above 300KHz.
Bass And Low End
Bass and low end frequencies need to be mixed in mono. This isn't an optional thing, they need to be centre, with no stereo or panning. If you do a mix with stereo or panned low end, then the cutting stylus will be forced into difficult/impossible movements leading to skips and ruined cuts (and possibly a ruined cutting stylus). Maybe this could be remedied by turning the bass off for the cutting, but it's unlikely you'll like the results. So - 345RPM will not cut recordings that have stereo or panned bass and low end.
Remove everything below 40Hz.
Make Your Recording User Friendly, Please
I will thank people (silently, even if not personally) who provide a detailed list of track times, running orders, what goes where etc all in one place. What speed you want. Anything you think the cutting engineer needs to look out for. The more info the better, and the more centrally gathered the better.