Before anything, let me define open chords as chords that has strings left untouched.
You must memorize the open major chords, which are C, D, E, G and A. These are relatively easy to learn; so don't worry. Then, you must memorize the open MINOR chords, which are Dm, Em and Am. These chords are like the original, except one finger is moved one fret closer to the neck. So they are identical to their relative major chord.
Memorize: C, D, E, G, A, Dm, Em, Am.
Here it might get a bit technical, but only to make it more understandable. A chord is considered a barre chord when one finger is pushing more than one string, by means of pushing the strings with not only with the fingertip, but with the whole front face of your finger (most likely the index finger/pointing finger). Also, a lot of people know that these "barre chords" can be moved around, but only some actually know what it means. It means that if you do an F-chord, then move it 1 FRET CLOSER to you, it becomes an F#-chord. Another fret closer again, then you've got a barre G-chord (which is equal to a normal G chord). This applies to ALL BARRE CHORDS, meaning also minor chords, 7 chords, etc.
SO, basically, if you master these 4 barre chords (F, Fm, A, A#m), then that means you also have mastered THESE barre chords Cm, C#, C#m, D#, D#m, F#m, Gm, G#, and G#m. FURTHER SO, that means you have master ALL MAJOR AND MINOR CHORDS. Amazing Isn't it?
This kinda explains why many people don't wanna learn barre chords just because they are "hard" or "painful," but it's worth it in the end. Barre chords are how those guitarists online know "too much"... Most probably those are barre chords.
Memorize: F, A#, Fm, A#m.
Here's how it works:
Do a normal A# chord. Notice how the "bar" finger is on the first fret, and all the other fingers on the third frets. Move it closer to you. Meaning, The bar chord on the second, and all the other fingers on the fourth fret. Then you have a B chord. Closer again, you've got a C chord, then C#, D, D# E, F, F#, G, G# then A, then A# again. It's a loop basically.
Just to make things clear:
1. When moving the barre chord, ALL the fingers move. Not just the bar finger, nor not just the normal fingers, ALL.
2. If you do an A#m position, all that follow it are minors also. Same goes with 7s, sustain chords, etc.
Notice how every letter has a sharp EXCEPT B and E? Yeah. Just don't ask why. So the loop is (relative to where you are starting) C, C#, D, D#, E, F, F#, G, G#, A, A# then B.
Just as I said earlier, learning only major and minor chords is absolutely fine, because I suspect it's only for jamming. But outside of that, 7 chords, sustained chords, augmented chords and stuff like that are NO DOUBT important. Use them and your covers are gonna sound exactly like the original.
A personal tip for you, when you keep forgetting the chord positions, find some chords on songs you actually LIKE. You're gonna keep playing this over and over and sooner or later you're gonna notice you've actually memorized it already.
Well that's chords in a nutshell, basically. If you don't understand a portion of this article, then read it again and again until you get it. Trust me it's WORTH IT. Thanks for reading, and have fun leaning. \m/