What does ScrumMaster do in Scrum?

“The servant-leader is servant first… It begins with the natural feeling that one wants to serve, to serve first. Then conscious choice brings one to aspire to lead. That person is sharply different from one who is leader first…”
– Robert K. Greenleaf

ScrumMaster is a ideally a full time role. Good ScrumMasters are people personalities, do not fear doing weird things, saying what is true . The main responsibilities
are

1. Keeper of Scrum Process – Teams and organizations have very less patience, They try anything for a few days or weeks and then there is pressure to do the routine stuff.There is a lot of pressure on the ScrumMaster to change the process too. Example, a manager will ask the ScrumMaster for metrics like Utilization, how each member of team is doing and micromanage. Good ScrumMasters like coaches do not give up easily. They keep doing Scrum by the book.
2. They are change agents.
3. Expose the mess and make teams impediments visible. – A scrum team, product owner and organization would have to work in unison to create great product. But they often work in three different directions. Good ScrumMaster protect the team by helping them not fear from the system and say anything that is an impediment.
4. Coach the product owner on “Working well as a product owner”
5. Coach the managers in an organization on “Leading well as an Agile Manager”
6. Coach the teams to become self organizing teams.
7. They keep the team together for years and fight off folks who want to steal team members
8. They are generally asleep when things are going well, but the first ones to arrive when things go wrong or people need help
9. There is saying that ScrumMaster is like the “Mom  of the house” – A thanks less job, yet it take a good patient mom to keep the house running
10. ScrumMaster facilitate Scrum Meeting
11. They are accountable that the Daily Scrum happens but they do not have to be always there
12. They maintain a impediment chart for the team in the team room
13. They set up a good task board, team room , burn down
14. They find a way for a distributed team to have the best possible collaboration tools
15. They sit where bulk of team sits and are aware of the team dynamics and issues in the team
16. They let the team fail and help them learn from these mistakes in retrospectives
17. Take the management along the journey. Many ScrumMaster do not work with management well enough. You need their support to succeed.
18. Be open to suggestions and feedback – even if this feedback is against your beliefs. Remember its not about you

More important than what they should do is what they should not do:

1. Do not be the star of the team. Let them shine. You are just the polish
2. Do not make decisions for the team
3. Do not become the teams bottleneck
4. Do not put pressure on the team.
5. Do not measure how much time they are spending per task. Yes this is true. Time is the worst possible productivity measure