I prefer the 1.5"x 2" sticky-notes in bright colors, but there are many sizes and tints to choose.
Any paper will do. I prefer pastels, with which I can differentiate the different acts of the book. (Say: four sheets of marigold paper for the chapters of Act I, five sheet of lilac for Act II, etc.)
Punch holes in the paper, stick the paper in a three ring binder and use one sheet per chapter (or per scene) and label your sticky-notes with the beats.