When you go to the gym and observe others, you see the same old classic style of lifting:
Splitting body parts into different days. A classic example would be like, chest/triceps monday, back/bicepts wednesday, legs friday, and abs somewhere in between.
This isolation style of lifting is extremely popular and most articles online give different variations to this same philosophy.
The thing is...
If you want to be as efficient a possible, you won't dedicate the majority of your time to isolated lifts.
You want to focus on the MAJOR lifts and create a simple LINEAR PROGRESSION program based on those lifts.
The cleanest example is a simple 5x5 program by Stronglifts.
You focus on the bench, squat, and deadlift exclusively and make sure to increment the weight slowly each time.
Are we saying to avoid isolated exercises? Of course not - you can add an accessory day to hit those smaller muscle groups.
However, if you want the biggest bang for buck in the gym, you go big lifts.