Great question! My advice on seeking an internship would be to make the most use of any career fairs that may be available at your school to seek employers offering internships and use the opportunity to connect in real-time. Keep an updated resume of your school accomplishments and any prior work experience and be sure to articulate why you are seeking the internship and how you can benefit the employer (e.g. employers often want to offer internships to someone interested in being a future employee!). After making the initial connection, be sure to follow-up and continue to seek any opportunity to expand your network over time.
Hope this helps.
When I finished my development studies I started a series of voluntary experiences worlwide, moving from Europe to Africa and Latin America. Obviously I was not getting paid, but mostly all organisations provided housing and food meanwhile I worked for them. After a while I started looking for internships in bilateral agencies or International Organisations and INGO. It seemed of all them valued the fact that I had some field experiences and I had been moving around different countries and cultures. It ease the path.
Hope is helpful anyhow and that you find what you are looking for!