Let's say the chords were:
4/4 [ D(Maj){1} ][ B(Min7){1} ][ G(Maj){1} ][ A(Maj){1} ]:
The {1} appended to each chord represents playing one full bar of each chord.
I would reduce the chords to a single note Chord Sketch using the Root of each chord. The above would translate into:
4/4 [ D[W] ][ B[W] ][ G[W] ][ A[W] ]:
(The [W] notation indicates to play each note for one Whole Note value, or 4 counts.)
I would then pratice this simplified sketch of the chord changes playing single notes instead of the whole chord. Over and over I would practice until I had the FEELING of the chord changes memorized.
What's the big deal, you say?
Well the Big Deal is that by reducing the complex chords into single notes, you can focus on memorizing WHEN to change each chord to get the FEEL of the chord changes. I would also sing the melody with my voice as I played the simplified chord sketch. Then only after I had the simplified chord sketch memorized I would then begin to fill in the chord sketch with the complete chord.
This way you are not trying to do everything all at once as you learn a new song. You first reduce the song into a simplified Chord Sketch in which each chord is represented by a single note. You then memorize the simplified Chord Sketch and sing the melody along with it. Finally, once the Chord Sketch is memorized you start filling in the Chord Sketch with the actual notes of each chord.
Almost like magic your fingers know what to do! Just think, if you tried to learn the chord changes all at once you would have to play all of the notes of each chord and change chords at the right time. This is difficult for beginners to do! However, once you have memorized the feeling of the chord changes by playing only the root of each chord, when you then start filling out each chord you have half of the work already done. It is much easier to focus on playing all of the notes of each chord AFTER you have memorized the chord change timeline of a popular song.
This strategy takes advantage of a special memory called muscle memory. You have three memories working for you as you play music. First, you have visual memory that represents the visual representation of the song. Next you have aural memory that represents your memory of how the song sounds. And then there is muscle memory that represents how the song feels to your fingers.
You may start off with visual memory get get you started, but it will be the muscle memory that you can depend on the most to enable you to play a song smoothly from beginning to end. Your aural memory will act as an alarm system that will alert you if you stray too far from the song's structure.