Measure your room. You should have able space to walk normally on each side of your bed. Also make sure that if you have any dressers or furniture with doors that they are fully opened when you measure. You want to make sure your new California King doesn’t take up your whole room!
Measure yourself! Yes, I know, this is a touchy subject but it has to be done. I’m not saying you should get on the scale, just got on your bed and if you have a spouse, both got on your bed. How much space do you currently have? Are you both comfortable? Do you have enough space to roll over? Can you move your arms? Many people that have Queen size beds realize that they have been sleeping awkwardly and not acknowledging to themselves they actually need more space.
Make adjustments for your bed frame. It’s important that if you are replacing you headboard that you to into account a larger headboard and/or bed frame.