Hi OP, new here so sharing about what works for me.

1. Understand the performance review process, expectations of you by your manager/company
2. A rating is a measure of your performance against the company's expectations of what a typical role at your tenure/experience can achieve
   1. If your role is expected to do this job at this level, and you did just that, that could just be meeting expectations.
   2. If what you did exceeds your manager/company's expectations of you, likely you can achieve better ratings
3. Work backwards =&gt; understand what exceeding expectations mean/look like for your job
   1. You can find out this info by asking your manager
   2. Observing what your senior do
   3. Observing what someone who got exceeding expectations did
4. Execute

In your case, looks like you were hired for a non-technical role but you are executing technically =&gt; this might be a mismatch of expectations/responsibilities between you and your manager. I suspect your manager is not expecting you to spend so much time coding for your non-technical role. 

Then again, clarifying the expectations with your manager is the most direct way of finding out how to exceed it i.e what would exceeds look like?