Don't know how much do you know of Chord theory so I'll give a quick review.
You take the scale of the chord. (a G chord of anytype is in G scale a C chord is in C scale etc.) the 1st 3rd and 5th note of that scale is your Major. So like, D major for instance is D, F#,A. The minor chord has a flatend the 3rd, so like a D minor is, D, F, A.
The sus4 chord replaces the 3rd with a 4th so Dsus4 is D, G, A.