Doors always open INTO a space, and "rest" against an adjacent wall. Interior french doors can go either way. A closet door opens out and towards you, unless a walk in pantry which would generally open into the pantry.

From My experience doors should always open into the room, example (bedroom). The only exception would be, one, the room is too small (closet) so would need to open out. Need to make sure when opening into a room the door doesn't open into the light switch plate make sure it opens opposite so there is an easy flow into the room. In order to change the door, you will need to take door and frame out. You will need to at least remove on side of door trim to get the door out. May have to use a saw-zaw if finish nails are put through trim and into door frame. Its really not that big of deal, I would saw (2) hardest parts are, one, not breaking the trim, and 2 shimming the door to open and close right. Hope this helps.

Open into the room,french doors are IMO the only ones that can go both ways ,Changing the swing of a door is actually a big deal .

I agree with the above for interior doors. you will want to get the swing of the door to open into a room in the least obstructive way possible. the one exception will be for coat closets and service closet doors. Changing door swings later is expensive for labor and material, so plan the swing carefully. However if you have a room with an exterior door you have options on swing out and often it makes sense to swing an exterior door out, you will want to make sure the door is ordered with security hinges if you choose this option.