How do you usually react when a person cries in front of you? Whenever I cry I would like to be left alone but if I leave the person alone it will look like I don't care

I might ask if there alright.

A small touch on the shoulder and a kind word.

Depends on how well I know the person. If it is someone I know well and know they need a hug, I will give them a hug. If I know they like their space, I give them their space. If it is someone I don't know, I will usually just ask if there is something I can do to help.

I don't know if you saw in the news the other day, but a lady was waiting in line in Florida for a generator. The sold the last one to the person in front of her. She just turned away and started to cry. She has a an elderly on oxygen and would need the generator to keep them alive during the hurricane. A gentleman saw her crying and gave up his generator so she could have it. When I saw this on the news I cried. 

I try to read their body language so I will know if I should step in and physically offer comfort and would words work better. If it's someone I don't know, I generally ask if they need any help, or if there is something I could do for them.