Not sure what you're after here. The obvious starting point is not to give anyone else your password, and not to share across the network any part of your filing system that contains anything you want to keep secret.
And then keep the machine itself under lock and key, because the above doesn't, of course, keep out someone who (a) is sufficiently determined and (b) has physical access to the machine. But nothing will keep out such a person - if someone has physical access to your machine and they really want to they will be able to read anything. Look up "evil maid" attacks to see how pointless it is trying to secure a machine that someone can physically get their hands on.
So, as with any security question, you have to start by telling us your threat model - exactly what are you trying to guard against, and what do you consider an acceptable residual risk?