I've done a good bit of research on Ghosts and such, and actually have come in contact with many as several lived in my house for a while.
Signs you might notice are things like
Cold or hot pockets of air
shadows from the corner of your eye or dashing across your vision
Objects breaking, gone missing, or moved
Strange noises or voices
even strange smells (a lot of people mention kitchen, cooking smells)
Doors opening or closing
Lights turning off and on or light bulbs burning out
TV/Computers shutting down
To name a few
Personally, you may feel
Tingling, usually on the back of the neck
hot or cold
The feeling someone is watching you
Becoming more angry or emotional than you usually do
Feeling like you were touched, punched, or pushed.
Everyone is different, every spirit is different and every haunting is different. Take you time and try to learn about it better, if you feel threatened by it - do look into banishing and cleansing. If not, you can find out what it wants and see if you can help it pass through.
Best of Blessings