I did actually try 2 approaches:
1. To try to shoot everything.
2. To stay (more or less) in one position and just avoid bullets + shooting things on my way.
Second one seems to wokr slightly better but some ships shoot still under certain angles - and those were generally getting me :D.
+ I think it should start slightly easier but over time become harder and harder - that would make the gameplay slightly longer for a shit players like myself :D