1) If you don't have a MagnetoSpeed or Labradar chronograph, zero at 100yrds then measure your drops at midrange (400-600yrds) to calibrate your velocity in an ballistic solving app.
2) if you do have a quality chronograph, trust it. I use a magneto speed distanced from muzzle same everytime using one of the spacers for consistency. I then trust that velocity. I setup a rifle profile for summer temp and one for winter temp. I then tru BC to get dope to match my ballistic solver.
Phone Apps
Phone App ballistic solvers almost all use the same math so pick your flavor or fashion of standard apps (Strehlok, Shooter, AB, JBM Desktop, BallisticsARC,etc).
I prefer the interface of BallisticsARC, hate the interface of AB. Have used both with equal problems as they use the same math but AB is relegated to just a bullet library for starting BC's.
I find the math on these apps to be pretty decent inside 800yrd but needs a separate truing at 800 if shooting beyond 1000 as the theoretic arc doesn't match up and you need two "humps" to the theoretical arc to mimic matching the actual arc of the bullet. These app's mathematical errors are like using dial calipers. Truing the caliper with a pin gauge gives you a window of accuracy before the errors build up to a noticeable level. You don't true a caliper with a 1mm pin to measure a 30mm part.
I find Trasol to be spot on for short and long range without recalibrating. Trasol uses completely different math as does Hornady 4Dof.
If you are using a "standard math" solver it is very important to use multiple BC's as these app algorithms heavy rely upon the BC number with changes with velocity. This is why Hornady and Sierra provide "banded" bc's. Banded BC's are like calibrating your calipers with numerous pins. If you are only using one BC input in your standard solver you are only calibrating your data for one set of distance. Faking your weather or velocity data to compensate for bad BC input or inherent error in solver math is not a solution in my book but seems to make lots if people happy to do so.
Trasol and 4Dof are not so reliant on the BC as such a significant component in the equation.
But don't take my word for it or anyone else's, test it out for yourself. Download different apps to see what User Interface you enjoy the most, then compare calculations from the different formulas (Trasol,4Dof, all others) and see how they line up with your real world data.