When you open Blender, you will see the default cube that it starts you out with. Your first reflex might be to delete it because you don't want just the defaults. However, you can turn that cube into your first 3D object with a little imagination.
You might remember from creating your first 2D mesh that each object in Blender is made up of a mesh, the edges, vertices and faces that make up the object. In Blender, you can add pre-created meshes by going to Add ==> Mesh and selecting from options like cubes, spheres, cylinders and a monkey head. If you add the monkey head and then go to Edit Mode while the head is still selected, you'll notice that its mesh is more complex than the simple cube with lots of edges and faces. Most experienced Blender users hesitate to create a complex mesh like that one using the point-to-point method. So they prefer to take a pre-made geometric shape like the cube and sculpt it into their preferred shape.
Creating The House
Making a simple house is a popular first project in Blender. First, open Blender and zoom in on the cube a little bit. Hit 3 on your number pad (Numpad 3) to get the front view. The cube will rotate so that you only see a single face and the top left corner of the grid view should say, Right Persp. The visible axes arrows should be only the blue Z arrow and the green Z arrow at this point. If they are in your way, you can eliminate them by hitting, CTRL + SPACE. Check to ensure that you are in edit mode and hit the Tab key if you aren't. Zoom in just a little bit more to get a clear view of the face.
In the above image, the button that my arrow is pointing at on the 3D View header is called “Occlude Geometry” to Python users and “Limit Selection to Visible” to us mere mortals who are just starting to learn about Blender. This button lets us see and work with vertices and edges that we wouldn't be able to easily access without rotating the view. Click on it once to get a translucent view of your object.
Resize The Cube
At this point, hit A on your keyboard to deselect everything. First, we want to select all of the vertices on top by right-clicking on the first, and then holding down the shift key and right-clicking on the rest. The selected vertices should be highlighted in orange, as in the above picture. Use the G button to Grab what you just selected, and then Z to lock them to the Z-axis. Now drag your mouse “upwards” to move the selected vertices along the Z-axis and make the cube taller. When the cube is at the height you wish, click anywhere outside the cube to ungrab it. Leave them selected for the next step.
Extrude is a useful tool for making copies of your selected vertices and pulling them out to create new edges and faces with the original vertices as the source. The selected items in the above screenshot are elements that I just extruded from the original elements at the top of the original cube. To use the Extrude tool, select the elements you wish to extrude, hit E on your keyboard, hit Z to lock it to the Z-axis if it isn't already, and drag your mouse along the Z-axis. In this case, this gives you new edges and faces in addition to your original cube. The extruded element will become your roof. When the height is where you want it, left-click to release the selection. Leave these vertices selected for the next step.
Make Your Roof Pointed
Right now, the house looks like a box on top of another box. To make your roof more pointed, hit W on your keyboard to bring up the Specials menu. These are special tools that you might not see on any of the menus you see when you open Blender. Select Merge, and then select Merge at Center. (You can also hit Alt + M for Merge to save a step.) The merged points will now come together at the top to form a pyramid, which is a fairly simplistic roof.
So this is my basic house. Later on, I could add things like windows and a door. For now, it just looks like an orange (all selected) Monopoly house. It is also hovering just above the grid, which I could change by selecting the bottom four vertices and extruding it out to form a foundation or grabbing the entire house by hitting G and moving it down along the Z axis.