Change the locks or have a local locksmith rekey them. There’s no telling how many people the previous owner may have given house keys. The easiest (and cheapest) solution is to have a locksmith rekey all of the knobs to the same lock, so you only need one key to open any door on your property.
Know the location of the main water shut off. The best way to do this is to ask the home inspector to show you where it’s located during your home inspection. Knowing where your water shut off is can save you thousands of dollars in damages in the event of a big plumbing leak, especially if your hot water heater fails.
Find the electrical panel and identify each breaker if they are not already labeled. There’s nothing more frustrating than having a tripped breaker and not being able to find the right one to reset.