Do you suspect you have a spirit or other entity in your home?
The first thing to remember is that every house, apartment, etc. has its own sounds and creaks regardless of the age. In addition to this, doors may not latch properly due to a shifting of the house or improper hangings when installed which could cause them to open on their own. With this in mind, here are some things to consider.
Not all spiritual visitors and hauntings are identical. While some may be aware of our presence and vice versa; other times our ghostly passerby's may be "stuck" in their existence and totally oblivious to our presence. In addition, unlike movies and other creations of horror for entertainment purposes, a spiritual visitor and/or haunting is not always obvious. Many times, the signs are more subtle and less recognized at first or over a period of time.
Please keep in mind that this is not a complete list, but it is a helpful tool to aid in considering whether or not you may have a spiritual visitor or a haunting.
ANIMAL BEHAVIOR
The senses of animals are extremely keen and are more fine tuned than we, the mere mortals. Your animal will act differently and will "talk" to you; just as they would if they needed to be put out to do their business. Body language is how they communicate. Pay attention. Are your animals avoiding a certain area or outright refuse to go into a room or near something (other than the bathroom where you bathe them)? Do they watch or stare at a particular spot where nobody is physically at but "something" has their undivided attention? Do they growl or raise their hair at something that you cannot see? Do they whimper, howl, whine, sound like they are in pain or being hurt when they are in a particular place or at a certain time of day; however are fine once they're away from that place?
SMALL CHILDREN
No, this is not a section about Carol Anne but small children, like animals, are more psychically in tune to other planes, dimensions and other things that cannot be physically seen with the naked eye always. If your child is telling you "the man is here" or "he/she is my new friend" or you even hear them talking to someone but you know they are "alone", just humor yourself and write it down. Ask questions. Try to get them to describe them. Drawing and coloring are great ways for small children to express what they see or feel so you could also have them make a picture of their newly found friend or of the visitor that they are seeing. Another great way to document is to get a "Nanny cam" or another similar device and set it up in the area (bedroom, living room, etc) where this activity seems to be occuring the most. However, the old addage there are no such things as monsters under the bed or in the closet should never be outright dismissed. Take the time to really hear what your child is saying. They might just have someone or something really visiting them.
SCENTS AND SMELLS
The olfactory system is an awesome sense that we all possess. Have you ever noticed the scent of a cologne or perhaps the scent of flowers when there are none present? Perhaps you do not smoke but there is a scent of pipe tobacco or a cigarette that catches your nose. Sometimes it might just be a passing scent that you pick up on only for a second and other times it might linger for a few minutes. If you cannot explain where the scent is coming from, you might have a spiritual visitor.
SOUNDS
Sometimes obvious and other times, quieter, sounds that shouldn't be heard, are. Doors opening and/or closing; drawers banging; pots and pans being rattled; silverware being rattled; scratching; knocking (like on a wall or door but noone is there); sounds of walking or climbing steps; these are common sounds that are heard when nobody is there to create those noises. Perhaps you hear giggling or an music from another era but no radios or televisions are on to produce the sounds. If you cannot justify a reason for the sounds you are hearing (water heater turning on, no drafts or windows are open to cause a door to open or close, etc.) and there are no squirrels or other wildlife critters running around in your walls or attic, it is possible that an unseen visitor is present.
ELECTRONICS
Your lights have turned off or on by themselves just out of the blue. Perhaps your television or your stereo turned back on after you turned it off or it was random in activating. Other electrical items can have the same things occur (mixer, blender - to name a couple). If you can rule out a surge or glitch in your appliances, lights and media equipment; understand that it is a possibility that someone or something is trying to capture your attention.
SENSE OF BEING WATCHED
Have you ever had that sensation that someone was watching you but you were alone? Have you ever felt the hair on the back of your neck or on your arms stand up? Do you feel uneasy being in a room or feel like you can't concentrate because "something" keeps catching your attention? If you can rule out the obvious and do not suffer from a mental deficiency, then perhaps something really is watching you.
MISSING OBJECTS
Time and again, we all misplace things - our keys, eye glasses, even a purse or wallet. Obviously, sometimes, when we are looking for something it is right under our noses and we don't see it but someone else will and the object or item is found. However, there is something called the "Borrowers Phenonmenon". For example: You put your keys on the desk but when later you go to use them and they're not there. You search high and low and cannot find them. A while later (moments, minutes, hours or even sometimes days) they reappear in the same place you know you left them. It is like they were used and then replaced when finished. When this happens, not even a total overhaul on your home cleaning wise and a dig through the garbage will not produce the object. It's gone till whatever or whoever decides to replace it.
SHADOWS AND OTHER SIGHTINGS
Out of the corner of your eye something catches your attention but when you turn to see what it was, it isn't there. Perhaps it was a shadow or a shape. Perhaps its was dark or on the flip side, someting with color or a transparancy to it when you saw it; but, nonetheless you saw something. Perhaps there is a "smokey" or "misty fog" you see for a few seconds. Maybe, you saw what you thought looked like a person but it was like looking at a semi clear image of someone instead; like a hazy outline. Or, maybe you have seen someone in clothes that don't seem to make the time period. In addition, perhaps it is not a "person" you are seeing but rather an "image" of a cat or dog, perhaps. Shadows seen while feeling like you are being watched are often passed off onto Shadow People (also referred to as the Shadow Person, Hat Man; amongst many other names pending on the region).
COLD SPOTS
Cold spots are often related to a spiritual presence. First you will want to rule out things that could cause a cold spot to be there. Are there drafts? Is it cold outside and the spot is by an exterior wall in your home. Once you have eliminated obvious reasons for this occurrence, it is quite possible that you are being visited.
PHYSICAL CONTACT
These are unexplained events of scratches, bruises, being tapped on the shoulder, hair pulled, being pushed, bedding pulled off of you, a stroke on the cheek, the sensation someone is holding your arm. When being touched, the sensation can feel cold as well as sometimes hot or even a "burning" cold. However, to receive a physical injury such as scratches, bite marks, or bruising is not a commonality and documentation via photo as well as where and when it happened is important to make note of.
Wonderful distinctions you have made in this post thank you for sharing! 
