Play chords in normal order, low to high: like "C-E-G", generally -- and then when it is necessary to consider changing the chord (consider usual chord progressions). The chord is highly dependent on which melody notes are being used in that part of the song. So an understanding of theory is helpful -- if for example: the notes of the melody are in the key of C (C-E-G) then you have the sub-dominant "4th chord (F)" which fits right in, or chord the "fifth chord (G)", and of course "B (the VII)" may work as it closely relates to "G7", and naturally D, F chords may be comfortable, all being in, of or near C Major.