This list may seem completely obvious and stupid to some, but because I am forgetful, I always check it when I think I am finished a house, just to make sure I havn't forgotten anything.

• Are the enough bedrooms?
  Big houses usually need more bedrooms. A huge house with one person living in it will seem silly.
  Bedrooms dont usually need much except for a bed, but you may wish to consider adding endtables next to the bed, a bookcase, a couch, a wardrobe, or a desk with chair.
  Sims can watch TV from bed, and have a computer or music player in the room, but be careful because these things can keep them awake at night.
• Are there enough bathrooms?
  If there are more than 4 people living in a house, you should have at least 2 toilets.
  There should be a shower in the house, and preferably a bath too.
• Is there a kitchen?
  A kitchen needs to have at least a fridge, some benchspace, and something to cook food with. It also needs somewhere to wash the dishes, and somewhere to take out the trash.
• Is there somewhere to eat food?
  You can either have a formal dining room, or just some counters and stools, but a good house should have an area where people can eat.
• Is there some sort of living room?
  Almost all houses in real life
• Can the sims raise their skills?
  You should try and make sure that the sims have access to objects in the house to build skills with. For example, a workout bench or pool for body skills; a mirror for charisma; a bookcase for cooking/cleaning/mechanical; a telescope or chess table for logic etc
• Is each room decorated?
  You should make sure each room is decorated the way you want it. This includes adding paintings/posters, and choosing the style of the objects.
• Is the house painted?
  Take a look at every room in the house, and rotate the camera around it so that you can make sure that every room is painted. Also remember to check the outside.
• Is there a roof?
  Take a look at your roof, make sure it covers everything it needs to. The AutoRoof feature can usually do this for you.
• Does each room have enough lighting?
  You need to check that each room has at least one light, and windows too if possible.
  And outside, you should at least have lights leading to the front door, and light any outdoor areas.
• Have you completed the terrain and landscaping?
  Make sure the terrain is painted the way you want it, that any hills are modelled, and that the trees are placed. If the yard looks empty, you may wish to consider adding a pool, garden or pond.
• Is the house safe and secure?
  Remember to add a burglar alarm to any room that is accessable from the outside. Any room with a fireplace, BBQ, or stove should have a fire alarm.
• Anything else?
  Garages, balconies, fences, pathways etc, can all be the icing on the cake of a good house.