Learning chords for the first time can be a frustrating process so you need to get maximum results for the effort you are putting in.
1) Learn the shape of the new chord as quickly as possible, this should not take long if you are making a conscious effort to do it. As soon as you have got the new chord shape in your mind cover up the chord box or diagram you were using and do it from memory.
2)Place your fingers in the correct places and strum the chord (take care to only strum the strings used in that chord), then pick each note individually and make sure it sound a clear note (when you strum it’s hard to pick put these clunks and muted notes). Then make any adjustments to your finger position and when each note is sounding clearly strum the whole chord again and get used to hearing the correct sound.
3) Three common problems with fretting chords are not having your wrist in the correct position on your fretting hand (if your having trouble try lowering your wrist a little), having your thumb on your fretting hand too high on the back of the guitar neck, and finally not having your fingers on their tiptoes as it were.