Like all muscle groups, before you start any back workout you should know where your weaknesses and strengths are. Now when it comes to the back it's kind of hard to know where your're weak since your head doesn't rotate 360 degrees. I found the best way is to get advice from someone that has a good understanding of what perfect symmetry looks like. (Ask a personal trainer with competition experience I'm sure they would love to help out.)
When you judge yourself, you can often convince yourself that you need to work on things that you simply enjoy doing. Do you need to work more upper lats, lower lats, traps, infraspinatus, reard delts? Figure out what needs to be a priority and place the first exercise in your workout to target that specific area because that's the exercise that will have the most benefit in your workout. Here are some great exercises to target specific areas. If you're not sure what all those muscles or exercises are use this.
Lower lats: Single arm dumbell row
Upper lats: Wide grip pullups
Rhomboids: Bent over barbell row
Lower traps: Incline front raises with thumbs up
Mid traps: Bent over lateral raises
Upper traps: Barbell shrugs
Infraspinatus/teres miner: Lying on side dumbell external rotation
Rear delt: Bent over laterals thumbs down
Spinal erector: back extensions
Now keep in mind that many exercises overlap different muscles and even though the back is the the most complex of the training day splits there's no need to do 40 sets in your back workout. Always remember this; "After you hammer a nail in the wall, all your doing is damaging the wall". Aim for 7-9 sets per muscle group whether it's directly hit or indirectly hit. So choose your exercises wisely.
