This page explain how to split 3D window and how to join two view into one, and how to change view direction.
Splitting the 3D window is to move mouse cursole on edge of the 3D window (See red box in following image), then mouse cursole will be changed. At that time, you press the middle button of the mouse. Menu will come up. Then, select "Split Area". After that, split line will show up. You adjust the line to your desired location to split, and then press left button of the mouse to execute the split.
During showing up the split line, you can change the direction, horizontal / vertical, by pressing "Tab Key", or middle button of mouse.
Menu

To join two windows into ine window is to move mouse cursole on edge of window. After changing mouse cursole, press middle mouse button, and select "Join Areas" in the menu. After that, as you can see following image, you can select which window is remained.Lighter window become remained window. And darker window will be removed.

It is necessary to change view to various angle in modeling. Blender has a pre-sets to change the view in the keypad,or you can change view from "View" menu in the header menu of the 3D window.
Following image is devided screen(1280x1024) to 4 windows and assigned different view respectively. If you want to use changed configuration as a default configuration when Blender activates, execute "File""Save Default Setting" in the main menu at the top of the windows.

| Keypad | View | Keypad | View | Keypad | View |
|---|---|---|---|---|---|
| 0 | Camera view | 1 | Front view | 2 | Rotate 15 deg to downward |
| 3 | Side view | 4 | Rotate 15 deg to left | 6 | Rotate 15 deg to right |
| 7 | Top view | 8 | Rotate 15 deg to upward |
If you use "Ctrl key" with above keys, that works as oppsite direction. For example, if you press "Ctrl+1", that is Bavk view.