Is there anything specific I have to do when swapping PC parts?

So I’m keeping the same motherboard but is there anything specific I have to do for swapping out RAM, GPU and CPU? And can you have two different ram kinda in the slots? (Example 2 Team Vulcan 8GB ram and 2 g skill trident z?) I plan on upgrading in the next year or so and I’m just curious whether there is anything I have to do before upgrading, all I know is I have to make sure the bios is updated.