I have found that sometimes things that look necessary on the first, second, third look turn out to not be later. For example, one 'declutter' task I was given was to get rid of the unnecessary items in the linen cupboard. On the Monday, there was nothing to throw. Same on Tuesday. On Thursday, there were a couple of items. On Friday, suddenly I had a box of items that I didn't need any more - it just took the looking over and over again to start separating out.

Other tricks - I know I get declutter/decision fatigue, so taking everything off a shelf, and then picking out the stuff that I want to keep, and then just get rid of the rest makes this easier. And restricting myself to a 'class' of items - this week I'm just going to sort out books, next week I'll look at clothes, the week after I'll look at toys. To mix this up, restricting myself to a room, and asking 'what is the most important?'.