Welcome to cdf. It's no big deal, you don't need a "guide". CloneDVD has a very intuitive splitting interface.
Just click on the "Scissors" icon in CloneDVD. The "Splitting Interface" will now appear. Easiest method is to deselect all titles except for the main movie. With the main title selected (and highlighted), choose a chapter split (with the slider bar) that is close to half of the chapters included on the original movie DVD. Keep an eye on the compression meter to ensure that you are at 100% quality on each of the split disks ... because some DVD originals have several huge chapters and several short chapters, so choosing a split at excactly half of the total number of chapters is sometimes not a perfect "data size" split split between the two backup media.
Then just re-select and juggle the smaller, xtras title sets between the two backup disks, as you see fit, in order to keep 100% quality on both backup media. If you have trouble (keeping 100% on the compression meter for either disk) you can then go back and readjust the chapter split on the main movie title till you get it the way you want it. ... like I said, juggle a little.
There are many different variations possible. For instance, some people will split the main movie on just the last couple of chapters necessary to keep 100% quality on the first disk and then pile all the special features and xtra title sets, along with the remaining few chapters of the main movie, onto disk2. There is no "right" way ... there is only a "your preferrence" way.
You can create a little more room on either disk, if necessary, by deleting sound and audio tracks that are not your native language. Also, be sure to select "Preserve Menus" for both split disks or your splits may not include the correct default functions required by your DVD player for flawless playback.