Look for weaknesses in your system.

If you are looking to push your corn yields, you need to look for weaknesses in your system.

• How is the drainage on your farm.  This can be expensive to fix, big payoffs can be big too.
• How is you fertility ?  David Wolfskill discusses planter setup in this Corn-Soybean Digest article.
• Do you know fertility levels?  Get a soil test or better yet, hire a consultant.
• How is your weed control.  Figure you have some resistant weeds and use residual herbicides and vary modes of action.
• Control insect pressures.  Scout and rotate.  
• Are you cheating yourself on population?
• What do you need to do for disease control? Are you using resistant hybrids?  Will you need fungicide?
• What are you doing for nitrogen management?  Soil testing, sensors, aerial sensing, and side dressing should be considered.

Maybe the list is overwhelming.  Pick one or two that you can improve.