The main point is to get it down on paper, computer screen, napkin, corner of a tablecloth which you're going to have to cut off and take with you---get it on something! Those thoughts are not warrantied to come back if lost.
I hear you on this one. Get it down on paper by any means necessary. When I was pregnant with my daughter and was caring for my son who was about 2 at the time, I'd clear an area of the living room and roll out a long piece of newspaper print with markers, crayons, finger paints etc. While my son went to town scribbing on one end of the paper, I was on the other end writing down bits and pieces of a story. I'd tear these musings off and staple them to my journal.