truth be told, this is my first sniper rifle and I've had it for about a month, initially i had a M14 SOCOM aeg with a custom milled rail to allow optic attachment. When i did my first test shoot I forgot that the hop-up needed adjustment, wherein i discovered my first problem - I can't see the bb to track its flight… So i can't figure out where to adjust to compensate. I was firing .25 green bbs indoor (probably why I couldn't see them) but I don't have an area I can just take the rifle to and spend a few hours tinkering with it. Past the hop-up, zeroing isn't difficult, I've zeroed my scopes before and i'm not concerned about that.
Other than that, I'd like distance training to gauge range prior to taking a shot, and I've done a lot of research about mil-dot calculations etc. That much is pretty much practice.