Do you have a room you can run into that (a) contains a telephone and (b) has a sturdy lock?
If you’re considering the absolute worst-case scenario, i.e. someone who has gained access to your place and is hell-bent on harming you, locking yourself into a room won’t help unless it has an extremely sturdy high-security door, which costs a lot of money and requires some difficult work by a skilled professional to install. Ordinary interior doors are not much of a barrier, regardless of what lock you put on them. (Not to even mention how fragile drywall is.)
I’m not an expert on home security, and I’m not familiar with all the details of your situation, so I don’t want to give any advice beyond my knowledge and competence. I’m merely pointing out things where I’m confident that the information I’m giving is accurate. It does seem obvious to me that if your outside doors and windows are reasonably well-secured, it will provide a stronger barrier than anything you can expect from interior doors without very extraordinary effort and investment. So I would definitely focus on the former, as far as security based on physical barriers goes. My impression is that reasonable measures like window grates should be sufficient deterrent for the overwhelming majority of potential intruders.
As for the other things mentioned by various commenters, like weapons, guard dogs, etc., even if I were an expert, there is too much that depends on your specific situation, from the relevant laws in your jurisdiction (for example, even mace is illegal to possess where I live) to your own physique and disposition.
NihilCredo:
If you’re considering the absolute worst-case scenario, i.e. someone who has gained access to your place and is hell-bent on harming you, locking yourself into a room won’t help unless it has an extremely sturdy high-security door, which costs a lot of money and requires some difficult work by a skilled professional to install. Ordinary interior doors are not much of a barrier, regardless of what lock you put on them. (Not to even mention how fragile drywall is.)
Okay, so given that I’m in an apartment and can’t fix those things, what should I be doing?
I’m not an expert on home security, and I’m not familiar with all the details of your situation, so I don’t want to give any advice beyond my knowledge and competence. I’m merely pointing out things where I’m confident that the information I’m giving is accurate. It does seem obvious to me that if your outside doors and windows are reasonably well-secured, it will provide a stronger barrier than anything you can expect from interior doors without very extraordinary effort and investment. So I would definitely focus on the former, as far as security based on physical barriers goes. My impression is that reasonable measures like window grates should be sufficient deterrent for the overwhelming majority of potential intruders.
As for the other things mentioned by various commenters, like weapons, guard dogs, etc., even if I were an expert, there is too much that depends on your specific situation, from the relevant laws in your jurisdiction (for example, even mace is illegal to possess where I live) to your own physique and disposition.