This question is pretty vague (as to what you are asking), and will likely be closed, but I think I understand your motivation, and I think it deserves an answer:
I have often said that 15% of people will do good work no matter what is going on, 15% will do bad work no matter what is going on, and the remaining 70% will meet expectations.
I am reading between the lines, a little bit, but it seems you are in the 70%. Your employer expects good work, and you deliver. However, your manager likely believes you are personally capable of being in that top 15%, and is trying to encourage you to become that.
The simplest and most visible change you can make is to try to envision yourself in the role of the previous and next person in the workflow of whatever you're doing, and ask:
- What would I expect to happen / be produced from this work?
- How will I know when the process is successful / complete?
- How will I know if the process failed, and why?
- What additional information or functionality would help me that's not in the requirements?
Now this is important: You don't ever want to go off-script from your assignment, but thinking through these scenarios and bringing potential improvements to your manager will go a long way. You'll gain insight into your company's business and culture. You'll develop an understanding of business processes outside your own, and demonstrate that you're (potentially) leadership material.
A personal anecdote as an example: When I was just out of college, I was the engineer of a post-production facility. As such, most of the equipment purchases went through me. Most of the "small stuff" was entirely at my discretion. I had to get purchase orders approved, but they essentially "sailed through." I realized that accounting was likely having difficulty understanding the bills that were coming in, as they weren't engineers, and the descriptions didn't make sense. I started making copies of the purchase orders and packing tickets, stapling them together (It was the early 90's. It was all paper.), and turning them in as shipments arrived. Just that simple step saved them hours of headache every month. It was a small thing, but it went a long way.
As for being indispensable: Don't try. Being indispensable is a threat to the business, even if you don't ever try to leverage it. A good manager will rid themselves of "indispensable" employees. What you want to be is valuable. You want to show that you are worth much more to the company than your compensation and overhead cost them. You want to be a resource of not only skill, but of information and insight, as well. A truly valuable employee is one that's not only an excellent individual contributor, but helps their colleagues become stronger and more productive, as well.
I hope I hit the main point of what you're asking.