1) Set saddle position. If you have no idea, then 0.883 x inseam will give a good idea of saddle height. The fore and aft position is determined by thigh length – a lot of people swear by kneecap over pedal spindle when pedals horizontal. Basically saddle should be in a position that the weight is taken through the legs. Ideally saddle should be level (unless a TT bike)
2) Once saddle is in the right position, then set bars. Saddle to bar drop is personal, I like 8 cm and am not fantastically flexible., spacers will raise the bar and bring it closer, reducing reach. Also shifter types can have a 1cm difference in hand position. Reach, is ultimately determined by body and arm length. Basically, put your arms on the hoods, lean over as into the wind, you want an elbow angle of about 90-100 degrees. So when resting on the hoods, you will have a little elbow bend to help with shocks and control. Stem length may need a change to get the correct reach.
3) Position of hoods. I normally loosen the bars and have people rest on the drops and pedal with their eyes closed (on a trainer). Lock bars at a comfortable angle – normally drops not parallel to the ground. Then I loosen and move the shifters for comfort and reach of the brake levers from the drops.
Common mistake is to adjust the saddle to adjust “fit”, get the saddle position dialled in first, and only then set the bars.