In order to be indispensable, you have to do great work. Unless you are self-employed or work for a boss that understand this, it's pretty hard to have the time to get stuff that matters done. Most of the time, you'll be occupied with busywork. Luckily, Michael Bungay Stanier (founder of Box of Crayons) offer us 7 ways to stop us from doing the busywork and do more great work. He categorizes the work we do into 3 different types. Bad, Good and Great work. The key is to stop doing or reduce time spent on the bad and good work and focus on the great.
The brutal truth is that if everyone is happy, then you're probably not doing Great Work - Michael Bungay Stanier