For the guitar, just choose easy songs you want to play so you can learn all the chords on a guitar.
If that's too boring for you, listen to the rhythm parts of songs and try to learn each chord for the progression and play it. Hotel California is a good song for learning how to hold bar chords and switching around.
Finger exercises are important too so just do 1,2,3,4 up and down all 6 strings using alternate picking making sure that each note is played clearly. You'll develop strong fingers like this
Hope it helps.