Christmas trees in April

So, my Christmas decorations have slowly spilled out of our storage room in the basement and are now threatening to take over my son's room (right next to said storage room). I have totes and totes of Christmas tree decorations, knick knacks, towels, blankets, pillows, village, Christmas tree, and verious and assorted other what nots that have slowly pushed my husband right to the edge. My question is, how do you decide what to keep and what to give away or pitch, and then, how to you store it so that it doesn't take up half your house?