I use a bit of a mental checklist when I'm clearing out clutter. You have to apply a little common sense, there are items that you need even though you hope never to actually use them (your first aid kit), and you have to be honest about the real likelihood of future use. This isn't always an easy judgement to make objectively (despite my post title). These questions, if you're straight with yourself, should help you separate the keepers from the goners. There's a good chance someone else could get real use out of the things you don't need, so think about friends and charities; recycle what you can.
- When was the last time you needed it?
- What is it's real personal value?
- Does having it make you happy?
- Does something else perform it's function better?
- Are you only holding on to it 'because it might be useful someday'?