What sort of inputs are required to make the project successful?

Sponsor and senior management support, strategic alignment, Business analysis, preliminary risk assessment, resource and other organizational assets availability

One of the most import input for a project to be successful is one that you receive from your team. Since team is the working directly on the project they know if any thing is causing the delay in project or if some thing can be improved that can benefit the project. It is recommended to have short discussions with your team members to get the exact picture of the task in process and for the upcoming requirements. This will also help in planning in advance if there is upcoming risk in the project like delay or quality.