Think long-term. Remember to plan not only for this stage of your life, but for the next phases, as well. If you're newlyweds planning to have children in a few years, take those future kids into account when planning your renovation, so that you don't have to redo everything. Ask people who already have kids what works in real life and what doesn't; what they wish they had in their living rooms; what has caused safety issues or got broken so many times it had to be thrown away.
Adding warmth and creating an inviting atmosphere can be a challenge for square living rooms. When all of your furniture is pushed up against the wall, which leaves seating far away from each other, you can make the space feel cold. But you can also make your square living room feel crowded or awkward if all the furniture is forced into one corner. Instead, float furniture away from the walls.