Best way to get it out, get something long that fits in the steerer but not through the star nut, and hammer it out from the top.
This works much better on steerer tubes that don't get narrower to the bottom. Echo steerer tubes do...
Best way to get one in, put a bolt in the top and be careful. It'll straighten up a fair bit so you have a bit of a margin for putting it in wonky. You're best to straighten it up as best you can before the second star goes in. Then you can whallop it.