You can create group filters in the Layer Manager when you have a lot of layers in your drawing. Create a group filter, make it the current group filter (it will be highlighted), and put only the layers you specifically need to be working with in that group by the drag-and-drop method. Using group filters helps streamline the number of layers to choose from when selecting layers from the Layers toolbar or ribbon. Note that if you wblock the drawing, any Group Filters that were created will be purged out of the file.
Notes from Cadalyst tip reviewer R.K. McSwain: Many people use layer filters based on layer properties, but as Michael points out in this tip, you can also create layer filters based purely on your own grouping desires. The layers you choose for a group don't have to share any common properties. Just select the ones you want and place them in the group.