Have you ever been working in a drawing with so many layout tabs in it that you feared having to go all the way to the Model tab just to get into model space?
Why not maximize your viewport from the tab that you're currently in and work in it as though you were in model space? You simply select the edge of the viewport that you wish to maximize, right-click, and select "Maximize Viewport":
You could also double-click on the edge of the viewport or click on the "Maximize Viewport" button in the tray to get the same results:
Note: if you are already in the viewport the right-click or double-click functions are not options to accomplish this.
Once the viewport is maximized you will be working in a temporary model space environment. You can pan and zoom to your hearts content. When you are done you can minimize the viewport and it will return to the view it was prior to the maximize.
To minimize the viewport, with nothing selected, you simply right click in the drawing area somewhere and select "Minimize Viewport":
Or you can click on the "Minimize Viewport" button in the tray:
When you've got a drawing with lots of tabs this little tip can be a real time saver.