When it comes to the basic equipment (knives, ladles, large spoons etc), anything not used within the last month can probably go.
When it comes to appliances, apply the month test - then think really hard about if it's something used less but actually useful and not cumbersome. I have an electric hand whisk and it does not get used every month. But it is very useful for when I need it, so I keep it, and that one item is not what makes the major clutter.
What should go are the unused machines that seemed like a great idea but get used once every 6/12/18 months, if that, and permanently occupy cupboards/worktops.
I also agree with Twerking what an odd statement about 2 for each person - glass, mug, plate etc. I did this recently and it has made a massive difference. You can't really use more than that! Also if you want to buy something new, seriously consider getting rid of something old.
Also be really honest about what gets used in your household. I've had a kettle on my worktop for years because that's just normal, right? Well, we hardly ever boil water. Because we're coffee drinkers. And we have a coffee maker. If we boil anything in a pan the water boils whilst in the pan. So, the kettle has been relegated to storage for a month to see if I think I need it during that time. If not, it's out.