1. Get an alarm system. Or install deadbolts, or get a guard dog, etc., just make sure you have some sort of protection between your home and the outside world. Even if you live in a safe neighborhood, it's always better to be safe than sorry.
2. Employ smart landscaping. It can be a pain to keep shrubbery and other landscaping in tip-top shape, but it will be worth it to prevent would-be criminals from hiding out in your bushes. A more open landscaping plan will prevent any bad guys from using your own property against you.
3. Never announce a vacation/trip on social media, or the Internet in general. With the widespread use of social media sites like Twitter, Facebook, and many others, it's easy to post about your excitement for an upcoming trip. However, it's very easy for a predator to see that you're taking a long weekend trip to visit your sister and decide to take care of some of your valuables for you. Do yourself a favor and don't post about your trip until after you return.
4. Have a few carbon monoxide/smoke detectors around your home. This one is pretty self-explanatory. Luckily it's pretty easy to find the two combined, but it's worth the investment if you have to buy them separately. Make sure you have enough to cover all of the zones in your house, and make sure you change the batteries at least twice a year. Most people change them when they change the clocks for daylight savings.
5. Stay up to date with home maintenance. Again, it can be a pain to keep up with routine maintenance, but it will be worth it in the long run. Whether it's termite/insect inspection or HVAC maintenance, or even plumbing check ups, it's worth it to keep these things in check. No one wants their AC to go out in the dead of summer or their water heater to bust a pipe and flood the basement.
These are the best tips I could think of. What else should homeowners be aware of?