Ooooh, this is a tough one, isn't it? Memorabilia generally boils down to two categories:
Stuff that evokes special memories for you and stuff that evokes special memories for other people, but somehow it's sitting on your shelves.
Let's deal with them separately.
Stuff that evokes special memories for you
1. Gather together your memorabilia and look it over. Do you see any trends? Does some of it "go together?" Start sorting it into piles, and while you're at it toss anything you know you don't need to keep.
Piles might include:
You get the idea
2. Try to look at your memorabilia with new eyes. How can you hold onto the memories without holding onto the actual "things"? Could you document the trophies with photographs and put them in one small photobook? Or could you arrange them nicely and take one large picture? When it comes to the small trophies little kids get for almost every sport these days, I leave them alone until I find them on the floor under the bed covered with dust. Then I quietly get rid of them. When the child is old enough to have worked hard for the trophy I keep them in a special place until that child decides on his own he's through with it. Adult children should keep their trophies at their houses.
If your collectibles suit you, fine! Keep and display them. If you're no longer interested in displaying them, it's time to find them a new home. If it makes you feel better, make an effort to find someone who really wants them instead of giving them to GoodWill. Better yet, sell them on eBay and pocket the cash!
I'm a firm believer in containing memorabilia. Things I keep: some schoolwork and art projects the kids have made. These tail off considerably when kids grow up, so even if you feel buried under artwork for the first few years, hang in there; the end is in sight. Every year I sort through all of them. As time passes I find it easier to sort out the masterpieces from the scribbles. I keep pictures that express my children's own character and creative writing pieces. I throw out "busy-work" stuff.
I only keep a few pieces of clothing for old times' sake. Otherwise I clear my closet so that I have room for new "special" outfits. I have a few baby clothes from each child, but little else. I do have my wedding dress.
Stuff that evokes memories for other people
Sometimes people are ready to get rid of things, but are held back by guilt. They assuage this guilt by passing them on to you, telling you how special the object is and how they know you'll like it.
I take these things with a smile and a nod. They live in my closet for awhile. Then they go to GoodWill. Most times the person who gave it to me never mentions it again. If they ask, I say, "It's packed away right now." I figure if you give me a "gift" it's mine to do with as I please.