Hi there, here is my answer to a similar recent thread http://forums.autodesk.com/t5/design-and-documentation/sketch-not-updating-when-bodies-moved/m-p/576...
"Hey there, this is definitely an interesting subject with a lot of ways to go about it. Besides creating the sketch and body in the desired location to begin with, I would say one of the most interesting ways to move everything, including sketches, while maintaining that location when editing a moved sketch, is the following. First be sure that your sketch is in a component, either by creating a new component and activating it so a new sketch goes into it, or creating a new component after the sketch is created and then dragging the sketch into the new component, which is normally allowed and also brings all bodies created from the sketch into the new component as well. Then when you want to move the body and sketch, do a Component Move, after which a snapshot button will appear in the upper right of the screen. This places an update/marker of new component position into the timeline.
"Finally, to make this new position exist before the sketch was created in the timeline [note this is only if you would like the sketch to remain in same place when entering/editing it, which is actually not usually necessary...also note can edit many things including dimensions and point locations without actually entering a sketch], you need to first insure the component creation event (a white cube) exists before the sketch creation event in the timeline. If not drag it back in time sufficiently. Then you can drag the snapshot event to before the sketch as well, and presto! Note that it's possible to also Combine components together, so fillets etc. can be performed between them.
Jesse