Assuming you didn't rank #1 for a term NOBODY searches for, you need to focus on your ON PAGE conversion
You can do this by breaking down the page into different elements
Focus on one element at a time
Do this:
Create variations
Test with traffic
See if there are any conversion improvements
Pick the best variation and try again
Keep doing this until you get the MOST conversions possible with that element
Next, move on to the next element
Let me know if you have any questions.