Once you have the general idea of the formulas down, its really simple.
C-D-E-F-G-A-B
1-2-3-4-5-6-7
8-9-10-11-12-13
Major chord is the 1-3-5 notes of the scale (see above). So Cmaj is C-E-G.
Minor chord is 1-3b-5 notes of the scale. Cminor would be C-Eb-G. For minor you just flat the 3rd.
To my understanding the 7th degree is always flat unless its specified as a Major chord. (I hope thats right :D). And the 3rd degree is only ever flat if its specified as a Minor.
So C7, is 1-3-5-7b. C-E-G-Bb
Cminor7 would be 1-3b-5-7b. C-Eb-G-Bb.
Cmaj7th is 1-3-5-7. C-E-G-B.
So once you get that, everything else afterward is even easier.
If you see a Cmajor9, that means you do 1-3-5-7-9. If you look above, anything past the 7th degree of the scale, you just start over on the scale and keep counting. So the 9th degree would be "D". 11th would be "F".
If you ever see Cadd13, I believe what that means is you do a Cmajor, and you add only the 13th degree (and not include the 7-9-11 degrees in the chord). So Cadd13 is C-E-G-A. Cmaj13 would technically be C-E-G-B-D-F-A, but that would be difficult on guitar, probably meant more so for the piano.
Remember if, you see a Minor, that means the 3rd and 7th degree will be flat (unless specified)
Cminor11 is C-Eb-G-Bb-D-F
CminorAdd11 would be C-Eb-G-F.
I would say those are basics, and man are there a boat load of some obscure ones. But once you get used to how the formulas work, you'll be able to figure any others for the most part.
Its easy if you keep in mind that the 1-3-5 is
almost always there. Thats what makes the suspended 2nd and suspended 4th unique. sus2 is 1-2-5. sus4 is 1-4-5. Csus2 is C-D-G. Csus4 C-F-G.
C6. Well it would be 1-3-5-6! C-E-G-A. Cminor6 is C-Eb-G-A. So on and so on, etc etc. Hope that helps, because that took some time lol.