What scale works best?

I've learned 7 different scales
1. Major
2. Dorian
3. Frygian
4. Lydian
5. Mixolydian and so on.

What kind of scale do i use on what cord?
I know that if you play a G minor cord it's best to use a g minor scale or a g minor pentatonic scale. what about the rest of the scales. What scale shall i use on a Em7 E7 Eadd9sus4and so on. I would be great if anyone could explain this for me.

First, welcome to the site, I see you're new, hope you enjoy yourself here.
OK, there is a long answer to this, and a very long ansew (kind of the length of several books).
Basically, each of the modes can be played over a couple of different chords, and different chords can take different scales.
If you want a jazzy sound, play a dorian scale over a m7 chord, but in rock it would be more common to play aeolian (the natural minor scale). For dom7 chords, play the mixolydian scale, but int blues you would play the minor pentatonic, as the interaction of the major third in the dom7 chord works well with the minor third in the pentatonic.
As for chords with things like sus4, add9, etc, the best hting to do is to work out what scale smay work yourself for each one. I'll give you a start. An Eadd9sus4 chord is a major chord with an added 9th and 4th. As these notes are not raised or flattened, you asre still playing a straight E major chord, which means you can play E Ionian (major) over it. However, most sus4 chords take out the third, so you could play a dorian or aeolian scale instead - making it a minor scale. The dorian scale has a major 6th, and the aeolian has a minor 6th. You wouldn't play a locrian scale or phrygian (flattened 2nd, which is a flat 9th where you have a natural), and you wouldn't play a lydian (raised 4th, whereas yours is natural). YOu could play a mixolydian though.
As you can see, it's a matter of deciding what notes are in the chord, and what scales they fit over.
Some chords you will find do not fit with major scale theory though, so you then want to look at the melodic minor scale. An example is a min/major7 chord, which has a a minor third but a major 7th.
A dom7#9 is also an example, where it has a major third and what appears to be a minor third, but in fact is a #9. Over this you could play the melodic minor scale a semitone above the chord note (ie a C melodic minor scale over a B7#9 chord).
However, there is another chord that works well over dom7 chords with a major third, that includes a minor third (the #9). That's right, the minor pentatonic. Typically, the 7#9 chord is used in blues, so you can merely play a minor pentatonic over it.
As you can see, there are lots of options. I hope I haven't confused you, but it can be simple if you let it be. It is quite fun,and I hope you can work it out. Good luck. If you have any more questions (say, about specific chords), just ask.

Thanks for your nice welcoming and help.
If i've got you right ( simplified )the only thing you have to do, is to analyze what tones there are in the cord and then use a scale that fit these tones. I'm i right?

You said if you want a jazzy sound on a m7 cord use dorian. Is this the scale most guitarist use on a m7 cord if they want to play without using the pentatonic scale? If this is correct what other cords are often used on the other scales?

Later, Kim

P.S
Do you have tabs of other scales? If, can you mail them to me on this adress. Kimnybakken@c2i.net

Since most sus4s don't have a third, this means that they're neither minor or major. They're mainly used as transition chords, so you can pretty much play anything you want over them (as long as it fits into the mood of the song).

By the way, if you try to look at each chord individually you're going to get into trouble. You have to look at the progression/song as a whole and figure out what to play over it and what will sound good. Figuring out major 6ths and minor 6ths and all that jargon is nice, but most of the time it's trial and error.

About your m7th question - it depends on the other chords of the song. Depending on what the chord progression is, you could play aeolian, phrygian, or even locrian.

As an exercise it's a good idea to learn the scale all over the fret board and then move to the next key, eventually playing the scale in every key.

You need to identify the 1st note of the scale in two places (i.e. the "c" note on the 3rd fret 5th string and the "c" note on the 5th fret third string. Use the "c" notes as anchors or bookends and play the scale within those frets. At first try to locate all the possible "c" notes on the fret board and then play the scale within the octave bookends.

After you have mastered that for a scale, select two octaves, and then three (use segovian scale fingering technique for moving up and down the fret board)

After you have mastered one scale (i.e. major) do the next scale. At some point you should be playing the scales anywhere on the fretboard.

The next thing you have to master is playing all the different scales in one octave location. For example, the "c" note on the 3rd fret 5th string and the "c" note on the 5th fret third string. Use the "c" notes as anchors or bookends and play all the scales within those frets (major, minor, relative minor, major pentatonic, minor pentatonic, all of the modes, etc...)

After you master all of the scales in one position for one tonal center (in this example "C"), do it for every possible key.

Another variation of these exercises is to sing the notes as you play them; sing and play every other note (play first note, sing 2nd note, play 3rd note, sing 4th note, ...)

I know this is a lot of stuff but it puts you on the right track to learn the fretboard, learn your scales, and develop your ear.

Good luck - this is a couple of months/years work!