make the bed
To neatly arrange the bed coverings (including sheets, blankets, and pillows) into their original position from before the bed was slept in. Please make the bed before you come down for breakfast. It's good to get into the habit of making the bed in the morning—it's an easy accomplishment to start your day!
make the bed (up)
1. To tidy or rearrange the bedclothes on one's bed after one has slept in it. Would it kill you to make the bed up in the morning? It only takes a couple minutes! I never feel like I've properly started the day until I've made the bed.
2. To prepare a bed for one to sleep in by fitting, arranging, or tidying the bedclothes on it. I made the bed in the spare room up, if you'd like to spend the night here. Be sure to make all of the beds up before our guests arrive tomorrow.