Show them the behaviour you wish to mimic. Let them have a voice. Keep communication open. Keep boundaries firm & follow through with threatened punishment. Never be physically violent with them.
Encourage debate. Alway show love, even if you don’t like them - toddlers & teens are trying! - comfort but don’t smother them.
Have fun. Laugh with them. Don’t hover around them constantly or become obsessed or knee jerk into action into at very perceived slight in school (ie don’t go into school shouting the odds if they’re not Mary in the Nativity, save your wrath & might for serious incidents, bullying etc).
Treat your children as equally as you can, but if you need to give more attention to one, explain & keep communicating your love to the others (appropriate to age, obvs).
Don’t let them roam the streets like teen wildebeest, have an open door policy so your teen & friends have somewhere safe to be.
Don’t compare them to other siblings/family/friends kids.
But mostly? Remember they are not there to fulfil and dreams or wishes that you may have had & not done. If your child isn’t academic, don’t force them to achieve goals like medicine if that’s what you do/wanted to do but didn’t. It’s a recipe for resentment.
Let them follow their own potential, support them & be there if it goes pear shaped.
These are a few things I’ve learned with 2 kids, numerous teen fosters & a lifetime working & volunteering with kids.
Of course, it may all be utter bollocks, but it seems to have worked so far 😂