Place a big box (you might need more than one) somewhere to throw all the giveaway items as you declutter over a period of time. Throw away what is no longer any good to anyone. Don't donate stained clothes for example.
Start with one place at a time and focus on that one place. No bunny trails. When you finish that one project go to the next when your ready
Finish the above said first project don't stop and get to it another day... if this is the plan before you start then pick a small project to do to start with so you can see real progress from day one. It will truly encourage you. Relax decluttering is an on going process.
Let it go. If you do not use it or it does not bring you joy or you never look at it but it belonged to someone you love take a picture and let it go.
Keep what you will actually use & what really really brings you joy apply this to everything from clothes to kitchen to hobbies etc!
As you declutter a place go ahead and organize what your keeping, this will make it easy on you later for retrieval!