The biggest thing about Ana is hitting Q’s and knowing that Q pierces while crouched, so utilize it. Also don’t always expect the enemies to stop moving so you can hit your Q. Its nice when they do, but they can’t always do that. Learning to hit moving targets with a skill shot will help you in the long run. She is very skill shot heavy.
Also, take the Sniping ult with channeled objectives, and take the Nano Boost with mages or ability heavy heroes.
I’m not too good with Ana, and I’m sure someone else can give better tips, but to me, these are just basics.