A successful abstract addresses the following points:
Problem: What is the central problem or question you investigated?
Purpose: Why is your study important? How it is different from other similar investigations? Why we should care about your project?
Methods: What are the important methods you used to perform your research?
Results: What are the major results of the research project? (You do not have to go into all of the results, only the major ones.)
Interpretation: How do your results relate back to your central problem?
Implications: Why are your results important? What can we learn from them?