E-Mailing supervisor during Masters Thesis - How often and how much? I am in a terminal masters program in the Humanities. I will have to write my masters thesis at some point and have been told that I will have 3 meetings with my professor.

I have never worked on a thesis or with a professor as closely as this (I did not write a thesis as an undergradute), so I am a bit worried about the whole process. 

What am I expected to do exactly? Am I allowed to email my professor with emails? Is it even expected? And if so, how often and much is appropriate between the meetings, and what can I expect to get out of the emails (as opposed to the meetings).

Sorry if this seems basic to some of you - it surely is. But it would be great to know if there are certain academic standards or rules I might not be aware of.
There is no standards about contacting your professor.

I think the proper answer to this is : ask your supervisor about it. Only he can tell you what he expects of you and how available he is. If you keep your email or contact with him civil and polite, their is nothing more to do. 

Depending on how many student he has to supervised and his working habits, he might tell you whether he prefers emails or meeting, or if he is able to make extra meetings with you should the need arise.