While most burglaries usually occur during the daytime when people are out at work, if they know a home is unoccupied during the nighttime, some will undoubtedly take advantage of the darkness.
If they are illuminated they may well be scared away or simply startled enough, perhaps thinking that they've been spotted.
Burglars are cowardly types and don't want to face life's hard challenges, so they take what others have accrued over a lifetime of hard work.
Secure doors and windows with good locks that cannot be accessed externally or through broken windows, and always make sure that they are locked whenever you leave the home or are going to sleep.
I'd recommend asking your local police for advice on securing your home, rather than letting a security firm take a lot of your money for little in return other than an alarm system that may or may not work when you need it most.
I'm sure they'd also recommend securing your garage door/basement access, because these places are often very easy to get in to.
If some uninvited guest does make it into your home, ensuring that your valuables are hidden is the best way to save them.
You can't do this with your TV's or audio equipment, but that needs to be insured anyway, preferably on an 'old for new' basis.
Hiding your jewelry, cash and so forth is easy; you install some kind of safe which is quite easily found (but not too easy) and then keep your most prized possessions elsewhere, leaving only a few dollars and inexpensive watches in the safe.
It's the "hide in plain sight" principle.
A simple burglar alarm can be purchased which is motion activated and many are wireless now, making them a snap to install.
Your local DIY store will have these in stock, and they can be installed with some of the most basic tools.
Most nowadays have a battery backup, so should power be cut to your home, they will still operate, and hopefully scare would-be thieves away.
Keep your blinds, shades or curtains pulled when you are at home at night so that people cannot see in, because some burglars have been known to reconnoiter for days before making their move.
The less they know, the more difficult it will be for them to burgle you.
Get to know your neighbors and make a pact with them that you'll call each other, or the police, should anything untoward seem to happen.
This is probably the single most important thing you could do to protect your home and its contents.