It's really important to share some information and discuss and decide a few basic things before you start an eTwinning project. Together with your partner(s) you should agree on
* project goals
* pedagogical contents
* the tools you'll use
* the timetable
Often this is done by sending a lot of emails back and forth. A more effective way is to create a project calendar and a common workspace for making plans together.
Very good tools for this would be Google Calendar and Google Docs. Both you can share with a partner and also publish in the net. They're very easy (and free) to create and use.
Google Docs is a great collaborative tool also for learning.