Chances of not getting through contract is very low. During this time, you should be able to sufficiently manage a class( Eg students are not fighting in your class, teaching and learning is going on). Showing responsibility as a teacher( Eg marking students work on time, content ams pedagogy can be improved in time to come) . Like earlier posts mentioned, Taking initiative to clarify and ask for help. One basic thing is also role modelling as a teacher, in appropriate attire and choice of language to students.

To be sent to NIE by 6 months, that will mean doing a cut above all the above mentioned. Meaning, the school is very sure that you will be able to do well as a teacher.