Yeah, locks are completely useless. My house had a lot of them, and the robbers just kicked the door or crowbarred their way in. House had cameras, alarms, etc, but all those were useless too, because my dad forgot to turn them on for the one night that they broke in.
Police were also useless; didn't bother to call the cops. Security guards were even more fucking useless, I've got a strong suspicion that they knew my family was out on vacation because of the security guards.
One thing that did work very well was barring the door. Not putting a big bar over it, just moving something heavy behind it so that they couldn't open it from that angle. Unfortunately, we didn't bar all the doors.
I'd advise strongly against guns too. You won't be able to shoot someone when they're in the same room. Seriously, unless you're highly trained with it. You can shoot them while they're breaking down the door, before it breaks, and you have to be extra sure that it's not your brother or whoever leaving their keys out. Also, robbers tend to work in groups, so if you've had enough time to shoot one, instead of them robbing you, they'd beat you up, rape you, and kill you for hurting their friend.
My best friend once scared off some robbers with a machete. Not as helpful as a gun, though.