What advice would you give to a friend suffering from culture shock?

The first one would be to try to don't be shy with people that you meet every day because they can give some advice to you. For example: how can you use your vocabulary as well as they know.
Also, always be accompanied by someone. If you're alone maybe could be more difficult to learn things.

What personality traits do you think could help prevent culture shock?
Definitely, be friendly!!!. If you're friendly and kind with everyone you'll have more friends and they can help you in whatever moment that you need them.

What variables might make culture shock more or less severe?
Maybe if you feel homesick, or if you miss your friends a lot, it can be a good reason to want to go home again.
Another thing could be the environment, the place you live, people, food, etc. those kind of things can do more difficult the stayed in a place.