Here are the questions with my answers and analyses after talking to a key 'witness':
Q: Do they come only at night?
A: No. They appear in broad day light as well. So, day, night, rain or shine, they can be there.
Q: How do they look like?
A: Most of the time, it is merely a shadowy blurry thing. If you have watched The Eye 2, the early scene of shadowy blurry figures surrounding a pregnant woman is close to the description. Interestingly, for baby ghosts (鬼仔 or toyol), they appear in a baby shape. There are generally 3 types: black, white and red. I think black and white are more because of the background just like dust on a black car appears grey and appears black on a white car. For red, that's seen as high energy or dangerous ones.
Q: Do they wear clothes?
A : It is blurry and so we don't really see what they wear. However, based on witness' account, he encountered a well dressed couple spirits who speak good English. It is still hard to say whether they should be categorized under spirits or angels.
Q: Do they appear more during Hungry Ghost period?
A: Nah. There is no special season.
Q: Can they appear anywhere?
A: Yes, they appear in houses, hotels, highways and also in holy places. Churches and temples have equal sightings of spirits (unless we don't categorize those as spirits). Jungles are full of them.
Q: What areas around Bandar Utama are considered hot areas?
A: Road between KBU and Kota Damansara appears to be high. The other one is the tunnel on LDP near KDU. Bukit Kiara is also worth mentioning.
Q: Why people who can say usually don't want to communicate with them?
A: Once the spirits know a person can see them, usually they will follow closely and try to communicate through these people. Even when these gifted people pretend they cannot see, the spirits will still do funny things to verify. They may suddenly appear in front of these people just to check if these people can see.
Q: Can they be reflected on a mirror?
A: Yes, they do cast an image on the mirror and they can sit in cars too.
Q: Can amulets or religious items ward off the spirits?
A: According to witness' account, they just flow pass as and when they like.
Q: Can they get into the physical world such as physical contact?
A: According to key witness' account, a person can feel their touching. There are also accounts of them reversing the orientation of the magnets (i.e. north to south pole), sounds of coins dropping between the ceiling and roof and gush of wind.
Q: What are the signs that a spirit is in the surrounding?
A: One sure sign is when the lights flicker.
Note: Spirits is a very subjective matter and I leave it to you to judge.
