1) Use the CV Curve tool or EP Curve tool to create a curve that resembles the profile of a teacup. Start at the origin and move up. See the illustration shown here for help.
[Since it'd be too hard to give you the illustration, here's the coordinates it gives, if you want them: (0,0) (-2,0) (-3,1) (-4,3) (-4,6) ]
2) Choose Edit Curve | Offset | Offset Curve On Surface. This will create a parallel curve.
3) At the top end of the curves, use the EP Curve tool to create another curve that intersects both of the profile curves, as shown in the following illustration.
4) WIth both curves selected, choose Edit Curves | Cut Curves. The intersecting curves will be cut into multiple peices. At this point, you could select any two of these curves and use the Attach Curves tool to connect or blend them.
[Here there is a paragraph which is saying why we're using the Fillet command instead of the Blend Attatchment Method. ]
1) Choose two of the resulting curve segments and delete the pieces of the new curve that extend beyond the intersections of the existing two curves, so that you hvae something that resembles this example: (illustration )
2) Before using the Fillet tool to create a round corner where these curves meet, it is important that you check the direction of the curves.* Maya will attempt to create the new curve in the angle of the U direction. For this reason, you may need to select one or both curves and choose Edit Curves | Reverse Curve Direction. Firgure 3-23 shows the curves before and after the fillet has been created. Notice the direction of the curves in the image on the right.
3) Now select both curves, and choose Edit Curves | Curve Fillet (options)
4) In the Curve Fillet Options window, reset the tool's settings to use the defaults and click Apply. You should see a new circular curve that transitions between the two existing curves.
5) If the operation failed, it is either because the curves were going in the wrong direction or the radius attribute in the Fillet tool options was set too large. Undo the fillet operation and try decreasing the size of the radius.*
* denotes possible solutions I've already tried. I may have done them wrong though, but I don't see how I could.