Switching Chords

A man went up to a policeman in London and asked "Can you tell me how to get to Wimbledon" and the policeman replied "Practice, practice, practice".
Same answer, sorry. What I do is practice with a sequence. OK, you want to learn the E7#9, so start by fingering the E7#9 chord, then strum it. Now, without stopping playing, fix the shape of an "A" chord in your mind, think of how your fingers will move from the E7#9 to an A. Once you have that firmly fixed in your mind, do it - make the change that you had in your mind. Now strum the A chord and think about going to the E7#9 - get the picture, clearly, in your mind, where will your fingers go and how will you move them, from the A chord, to the E7#9. Only when you have it very clearly in your mind should you make the move (and don't forget to keep strumming all the time).
Now try moving from the E7#9 to a B7, using exactly the same routine - fix the B7 and how your fingers are going to move to it firmly in your mind. Now move to the B7. Then using the same routine, go back to the E7#9.
Now, go throught the same procedure with C, D, E, F and G.
Strum all the way though, but you're not trying to make music, you're learning to change chords, so it doesn't matter if you strum one chord 5 times or 500, you continue strumming it until the image of the next chord is firmly embedded in your mind. It is the imagery that's important. Keep doing that (for any chord for that matter) for a while and you'll find the changes start to get quicker and easier.
No matter what the target chord, that you're wanting to get to grips with is, the sequence is the same:
Target, A, target, B(7), target, C, target, D, target, E, target, F, target, G, target.
If you want to use other chords, that's fine. You could change it to
"target, A7 target, B7, target, C7, target, D7, target, E7, target, F7, target, G7, target" or
"target, Am, target, Bm, target, Cm, target, Dm, target, Em, target, Fm, target, Gm, target.
You use barre chords or whatever you want

Greybeard has it right. Just practice repeatedly fingering and un-fingering the chord then going to and from the chord and eventually it will be automagic.

What I do is practice with a sequence.

Greybeard is a GENIOUS!! That is exactly what I do too.

When you want to learn anything on the guitar you need to break it down into managable sections. If you want to learn a song but cant form the chords yet, its worthwhile (and important) to learn the chords first by doing what GB said above. Need to get the strumming down, ok same thing but now focus on the strumming.

But like GB said visualize the next move and practice only on the chords and changes not on the strumming. One thing at a time.

Geoo