Most break-ins are crimes of opportunity, so the goal of home security is to make your home a harder, less appealing target. Many of the most effective steps cost little.
Doors, locks, and windows
Solid exterior doors with deadbolts and reinforced strike plates resist forced entry far better than the short screws that come standard. Lock windows and ground-floor sliders (a bar in the track helps), and don't hide spare keys in obvious spots.
Lighting and visibility
Motion-sensor lighting at entries and dark corners removes the cover intruders prefer, and trimming shrubs near windows and doors eliminates hiding spots. A well-lit, visible entry is a strong deterrent.
Cameras and habits
A visible video doorbell and a camera or two deter and document. But habits matter as much as gear: lock up every time, make the home look occupied when you're away (timers on lights, holding mail), and don't broadcast vacations on social media.