Firstly, I am a complete beginner. I've been using Windows for all my computing life. I'm confident about installing Linux as I've done it before, however I am about to buy a new laptop and it will have a 256GB SSD and a 1TB HDD.
I want the option of installing other Ubuntu variants, but will begin with standard Ubuntu and need some detailed guidance on how to configure the partition correctly. I've seen a few guides on this site and elsewhere, but they all seem to assume some prior knowledge and make assumptions that you know something when you really don't.
I need an idiot's guide to how to configure the installation of Ubuntu on a new machine whilst allowing for the installation of one or more other Ubuntu/Linux installations at a later date. I am wondering if I should install Ubuntu on the entire SSD and then, later, I can install another Linux system on the HDD, or would it make more sense to partition the SSD and put a couple of Linux installations on it? In which case, I need help with setting up the first partition for the first installation of Ubuntu to both optimise it, and allow for the other variant's installation later.