Ensure your derailleur cage can support the largest cog you want. After that pick the range you need, especially if you’re going 1x. 52/36 or 50/34 with 11-28 would cover (best guess) 95% of the gearing range for any condition. Exceptions obviously for large front rings (descent from Hawi or anything in excess of 40mph) or dinner plate 58/60T TT use to mitigate chainline friction loss.

Edit: You can also play with calculator at http://www.bikecalc.com/speed_at_cadence to confirm your selection.