Not all locations will allow pets. Familiars cannot journey into far off places, and traversing from one town to another will cause the familiar to become lost as you travel from one large area to another, even if the familiar is following you.
Familiars are very good at finding people who are located in an area in which they can be found. They can also be commanded to move from one room to another, but they cannot open doors or go into a lot of places the way you or I would. They usually have their own ways of going around such places and locating a person on the other side anyway.
Familiars can watch and listen to the events happening in a room as they happen. They can also speak the words we command them to, and they can pick up small objects.
Typically, upon casting a successful call familiar spell, we will tell the familiar to watch. Then we will tell the familiar to find somebody. If that person is findable, the familiar will trot off looking for them.
Sometimes they are findable but not accessable, like sitting at a table or inside a building that a flying familiar cannot get to, or invisible. In that case, the critter will keep looking for the person but will not find them until they emerge. If you tell your familiar to return , the familiar will look for you and try to find you. It will not find you if we are invisible or inaccessible. It will just keep looking.
If the familiar finds the person, we tell the familiar to look. He will show us the room he is in, complete with the person he found. If the person moves around, the familiar will stalk them in a manner similar to the way that a floating disk tracks after us as we move about.
We can tell the familiar to say something, we can tell the familiar to return to us, and we can tell the familiar to go north or up or out, or any other direction. They will do as we say if they can.
When the spell works, it creates a misty portal of fog that we can move through. We simply go mist. We cannot move our group through the mist. Everybody must go through the mist of their own accord. The portal does not last very long, and it fades very quickly once someone has gone through it.