I would start with the obvious stuff like newspapers and junk mail that won't hurt. Bag them and recycle them. Do not think, as a friend's mother does, that there will be something interesting to read that you have missed, as in the old days there was something interesting on the chip wrapper, even if it was a paper you took. There won't be, or you won't read it. I have been a bit guilty of this myself, as my paper is large and has a lot of stuff in it. Last week I threw out four bags full for the bin men. Except that I was so busy packing the bags that I missed the lorry and had to take them to the dump myself.
While my friend's mother was in hospital, I threw out not only newspapers, but also loads of estate agents' magazines - turned out she kept those for the photos of historical local buildings. Ooops. But she didn't cut the pages out and file them, just left them mixed up with everything else - how was I to know they weren't just junk mail?
She doesn't want to declutter. She uses it as a wall. If you do want to declutter, most of the hard work is done.