There are several factors for establishing a civilization which are:
Big population centers: These help people survive with the help of each other, like farmers can grow and sell in these areas etc.
Monumental Architecture or Art: This will be identified as their legacy
Record Keeping: This can be a language or any other recording system to help record the history and traditions.
System of administering areas: Help run the place smoothly.
Labor division: Various people are skilled at various jobs, to do a certain job a skilled laborer is required.
Social Class System: It can be based on wealth as well as the type of work performed.
In order to become a civilization a society needs to bring all these attributes in and work towards a common goal of achieving them.