On samp i always found this:
0-100 ping of opponent = aim 1 step in front
100-200 ping of opponent = aim 2 steps
200-300 ping of opponent = aim 3 steps
300+ ping of opponent = Run for dear life!
Always lead aim and make your movements as random as possible, as others cannot lead aim you.
With this you should hit a fair few players - not all though.
Oh and go against the best. I did all the time, i was persistent (seriously, i would go into 3 v me, get killed and go back for more!) but when you go against the people again you get a little better, etc.