There are a few rules here.
Rule #1- there aren’t any rules. You’re probably thinking, “Well wait, why talk about rules if there aren’t any?” Let me explain. The rules are not set in stone. These are general guidelines for different styles of music.
The first thing is your guitar. The type it is affects the tone. I use a Washburn OE-30, which is a semi hollow body. Unfortunately, I don’t think this guitar is made anymore. But there are many semi-hollows out there. The reason I like them is they have a very versatile sound.
Rule #2- To find the sound, you have to determine the style. Jazz is a very versatile genre. Some of it sounds bluesy, some country, some like rock, or maybe its own unique sound. When I practice jazz by myself, I usually just play clean. A clean semi-hollow has a very bluesy sound to it, which is why I like it. A solid-body clean has more twang than the semi-hollow. It’s still a usable sound, but for a true jazz sound out of a solid body, it’s best to use effects, like a Tube Distortion or a Blues Overdrive.
Rule #3- The instruments being played makes a difference. When I play in public, it’s mostly at church. At one church where I play, the main instrument is an acoustic guitar. I play with a very slight overdrive with a treble heavy equalizer. This gives the guitar a twang similar to some country songs. At another church, the main instrument is a piano. When I play there, I use more overdrive, and a little more midrange and bass. This is because the piano plays the melody line and I don’t want mine to be twangy like the highs of a piano.
Rule #4- If you want to create your own sound, or want to be able to replicate many different styles and sounds, you’ll need the proper effects. You can buy an amp with effects built in. It’s cheaper and easier to transport. But there are three big disadvantages. One, you can’t layer them. You can’t turn on multiple effects to get some really crazy sounds. You can usually only have on one or two at a time. Two, on most of them, you can’t turn them on and off during the song. Some of these amps have footswitches with them, but that’s usually only the very expensive ones. You have to set the effect and leave it on for the whole song, then walk back to the amp to switch it for the next one. And the last thing is most of them sound kinda fake. They don’t have as good of sound quality as individual pedals. If you want to buy effect pedals, here’s a list of good ones to have on hand.
1. Distortion- there are many different ones, so it’s best to get a couple different ones
2. Flanger- This effect gives some fantasy sounds to it. It’s great for background noise during voice overs and intros.
3. Tube- Like the distortion, there are several different types, but only one will do, since most of them are the same. Good for smooth jazz and Chicago Blues.
4. Wah- You only need one, but there’s a wide variety. I prefer the ones made by Morley because rather than just being on/off, they have a rocker pedal, so there’s a wider range of note bending.
Rule #5- Effects can get expensive, so just buy one or two at a time. By7 doing this, you develop your own unique sound slowly over time. Your uniqueness as a musician doesn't happen overnight. Even if all you do is play someone else's songs, rather than writing originals, you still have a sound that's YOU. It what makes a person identified as an artist.
So far, you have scales to play lead, and now you know how to get the proper sound. Just always remember that music is an art, and art has no rules.