It is not a good idea to leave a pool of water on your hardwood floors. The cracks in between the hardwood will absorb the moisture and swell. If this happens in even a little spot it will still be noticeable. If any liquid is spilled on the floor you need to soak up the fluid right away. When you clean your hardwood floor you can use a damp mop but only damp. You may want to use a floor cleaner for hardwood. Whatever you choose you must use only a damp mop.
Another thing that can happen to hardwood floors are dents and scratches. High heels are torture to hardwood floors. Over a long perios of time furniture legs cause dents and scratches also. You can choose to put area rugs under the furniture to protect the floors or you can put felts on the bottoms of the furniture legs. Also you could add some area rugs to the highly traveled areas in your home such as kitchens, hallways, in front of the couch.
Some homeowners like the character that scratches and dents give the floor. But when you feel that you are in fact sick of them you can get your hardwood flooring refinished. You may need to have your hardwood floors refinished every ten years or so, this will also add a protective top coat to your hardwood floors. Moving anything across your hardwood floors to letting your dog run in the house can cause scratches and dents.
You may also consider installing a heating element for heated floors Another tip is is to buy a pneumatic floor nailer if you like DIY projects.