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1.) Spirits like to be in corners or prefer corners.
2.) Spirits feed off of emotion.
3.) Spirits can go into the past or future and even be in the present.
4.) Sometimes - spirits leave behind "smells".
5.) Sometimes - spirits leave behind "dirt" or other strange things.
6.) Spirits can tell when you are trying become aware of them: and because of that - they usually do not allow you to catch them on camera, it has to be on accident - that they may be captured on camera.
7.) Spirits prefer to communicate with us through our dreams, but that preference will not stop them from trying to communicate with us anyway.
8.) Spirits need energy to manifest, and if it only has a little bit - it can only appear in one frame at a time, which is very difficult to spot.
9.) Spirits are fond of nature and usually prefer to be near bushes or trees or dirt; if they are not in a house, e.t.c. - but... that preference will not stop them from being around unnatural places.
10.) Spirits can do things for you.
11.) Some spirits are protective and want to help or guide you.

And that is all I know so far. ~

Is there anything else I am missing?

When spirits manifest, you already mentioned they need energy, the temperature might drop a couple of degrees. I've also noticed some changes in humidity strangely enough...
Spirits can be "trapped' in locations or attached to items. I have a mirror that's been in the family for ages and it means a lot to me because there is a protective spirit attached to it that is like a brother to me.

I'm certain there is more...I'll think of it eventually.

7. prefer isn't really the correct word. it's easier through dreams then the busy of daily life