In real estate, buyers buy space. The more space you're able to show, whether it be living or storage space, the more you'll be able to sell for. Unfortunately, that's easier said than done. Most people are pack rats. Rooms have too much furniture and you'll find stuff overflowing in every nook and cranny. There's little space for walking sometimes, much less for living.
Decluttering is the process of reclaiming the space in your house from years of collecting and storing. Don't expect the buyers to ignore all this and imagine your house in its clutter-free state. Buyers sometimes see dozens of houses in one day and their brains are overtaxed. Declutter so the buyers can see your house, not your mess.
If you do nothing else to improve the value of your house, at least do this. Remarkably, decluttering is free (it just takes time and elbow grease) yet a lot of sellers don't put enough effort into it! To re-iterate this important point: buyers buy space in real estate.
Here are some advice and tips to get you moving,