I searched a lot to find a tutorial for drag & drop with jQuery alone (without UI), but due to the popularity of JQuery UI, all drag and drop features are based on JQuer
I think a good starting place might be to map out the process, and then decide which jQuery tools you will need to use for each user action.
so the user process might be:
which needs the following types of event listeners:
At the very least. Another option might be to check out the jQuery UI source, and see how they do it! Which will tell you exactly what to do but you can add to it or trim where necessary.