well wat u can do as a great excercise is a major scale for instance gmajor. third fret 6 string and just play the first 4 notes g, a, b, c, b, a, g. but use each finger ie.
g= 1st
a=2nd
b=3rd
c=4th

once thats done throgh picking try hammering on. i e g,a,g,b,g,c
do this ten times each time u start playing and soon enough u will get stronger more dexterous and be able to stretch better. ps always excecise clean so u can disictively hear every note.