This tutorial requires some basic knowledges of Blender: how to deal with views, mesh and Bezier Curves.
The steps required to make a "spin" object are well known and covered in various tutorials, let me recall them quicly:
1. Make a profile (mesh) object
2. Set Degr to 360 and Steps to a reasonable value (eg. 32) and press Spin
3. Click on a window set to top view and you have your nice spin object!
4. Select all your vertices, then Remove Doubles to get rid of unnecessary vertices, Recalculate Normal Outside (Ctrl+N) to prevent rendering artefacts and Set Smooth (in button window) to look smooth
This method works fine, however it's not much flexible: after step 3, if your spin object doesn't look good you have to Undo, edit the profile and then repeat the spin. In fact you have to repeat these steps many times in oder to achieve a good result.
It would be nice if you can edit the profile and see the modifications applay to the spin object in real time. With the next technique, faturing Bezier Curves, it's possible and even easyer: your profile is a Bezier Curve, easyer to shape than a mess of polys.
1. In top view add a Bezier circle (Add > Curve > Bezier Circle)
2. Don't resize it (neither in Object Mode nor in Edit Mode), just zoom a little bit to see it properly
3. Switch to front view (Numpad 1) and add a Bezier Curve (Add > Curve > Bezier Curve)
4. The curve is here
5. Translate the curve in Object Mode to the left so that the center of the curve (the pink fat dot) lies exactly on the circle (use Ctrl key when moving so you can snap to grid lines)
6. Give to the curve object a name you can easily remember (since we're going to create a glass we can call it "Glass BO" where BO stands for Bevel Object)
7. Now select the circle...
8. ...and type the name of you curve in the BevOb field.
9. Et voilà... we have a nice 3D object featuring a curve rotating around z axis
10. Shape your curve to whatever you like: you will see your changes take place immediately in every view. Since your Bevel Object is a Bezier Curve you can add or remove control points, create corners or keep it smooth much easyer than with polys...
11. But, wait a minute... the glass is closed! Blender caps your curves by default, if you want to open it...
12. ...select the circle, i.e. the glass (not the curve!) and turn off the "Back" and "Front" buttons
13. Tip: if you parent your Bevel Object to the circle you can easily translate, rotate and scale everything keeping always the ability to "edit in place" your object
14. Note that Blender performs automatically a curve-to-mesh conversion at render time, so your curves will always be rendered as polys. You can control the subdivision amount playing with the DefResolU value of the profile curve (defining the profile resolution) and the same for the base circle (setting the number of steps of your spin). After you insert a value you have to pres the Set button and maybe enter and exit Edit Mode to view changes.
15. I you want to do some mesh editino or UV mapping you can always convert your object to a Mesh with Alt+C (remember to remove doubles and recalc normals outside), obviously you loose the ability to reshape it in "real time"
