I'm going to go against the grain here, but "room by room" never worked for me as I would get so overwhelmed trying to tackle a whole room at once. And inevitably I would end up moving things into other rooms.
I am currently de-cluttering because I am expecting a baby and am tackling my house according to category. As an example, yesterday my category was "Shoes" so I went around the house collecting all the shoes lying around, under the stairs, bottom of the wardrobe etc.
I gave them all a wipe down if they were dusty, a spray of fabric freshener if necessary and then sorted them according to those I was currently using regularly (due to season). I put all my current shoes in the downstairs shoe rack so they are accessible. And the rest in boxes at the bottom of my wardrobe and labelled them so I know what's in each box. I threw away a few pairs I don't wear any more.
Today I am doing "Cards" which means going through every drawer and box in the house finding old birthday, anniversary cards. I tend to just put them in drawers and they don't really have a home. I also had all my wedding cards somewhere and a few childhood ones. I went through every single one and kept only the most sentimental ones (30th birthday from my grandparents for example) and found a box to put them all in. Now when I next have a birthday I will choose my favourite few cards and file them away.
I know I've been quite detailed and it sounds quite labour intensive but honestly it doesn't feel overwhelming because I'm not trying to take on an entire room full of different types of object, clothing etc.
Other categories can be "Blankets" which would involve going round the house, collecting all blankets, throwing the ones that were a bit yuck and washing the rest and returning them to their home i.e. bed or sofa. So it doesn't have to mean throwing away sentimental stuff at first.
Let me know if you think that would be manageable and I can share a list of my categories and how I organise them?