Once you have defined your indicators, you need to collect the data that will allow you to measure and compare them. You can use different sources and methods of data collection, depending on the availability, reliability, and validity of the information. Some common methods of data collection are surveys, interviews, focus groups, observations, document reviews, or tests. You should collect data before, during, and after the change implementation, to establish a baseline, monitor the progress, and evaluate the results. You should also ensure that the data is accurate, consistent, and representative of the situation.