You'll be too consumed with planning to care about making an impression.
Don't hog the photocopier
Arrive super-early
Find out which children in the class have SEN and read their IEPs/ equivalent. Ask how best you can support these children.
Remember, some children with SEN (and some without), find it difficult to have a new adult in the room. Be sensitive to their anxiety. Most children will love you immediate and be vying for your attention. Those who don't, need plenty of praise and specific positive comments on their efforts and abilities. This will help them to feel less anxious.
Particularly tricky behaviour: make this/ these children your helpers during delivery time. Make them feel liked. They will be less anxious and follow your direction better, as a result.
Convey confidence.
Develop a 'teacher's voice'. (Project)
Follow the ways of your mentor - and retain or abandon good / bad practice when you move on.
Buy a Frixion pen(s) in the right colour for school marking (and conceal it about your person).
Warn your family and friends that you're not emigrating bit may not be contactable for the next six weeks.
Be prepared to get really very poorly, not get much sleep and work harder than ever.
Remember that it gets easier.
Observe who sits in which chair when in the staff room. Chairs won't have names - but they may have 'owners'.