This is often impossible to eradicate. The more frequently a response is practiced, the better it is learned and the longer it is remembered. The opposite is also true. The goal is to develop in students the same ability as that of native speakers. L1 should be banned from the classroom.
Students learn best through a stimulus-response technique.
Pattern drills are taught without explanation. Discussion of grammar should be very brief. In developing the 4 skills, follow the natural sequence of L1 learning. Language is speech, not writing. Language is a set of habits Teach the language, not about the language.