Your e-mail address should be clear for recipients, unless for some reason you wish to conceal your identity. Most of the time fantasy names do tell a lot about their bearers, so the best option is to keep your own, far less revealing real name.

The subject line must be completed, first because it helps your reader immediately grasp the gist of your message, second because it allows the recipient to sort out incoming messages for future handling and relevance.

Openings and closings do exist in an e-mail environment, although beginners tend to confuse the relative informality prevailing in email etiquette with downright absence of etiquette and discourtesy. Salutations and complimentary closes should roughly follow the rules below. Phrasing may be nuanced as the relationship warms up over time. Just observe how your partner handles the situation.
If on unequal footing, ie as in student-teacher correspondence, the best is not to deviate from the proposed pattern:

There are rules regarding proper typing and spelling. Observe them, lest you be taken as a moron or a primate.

People use the e-mail to gain time. The rule is to convey information in as compact a form as possible. Avoid lengthy pages. Observe: the average message is 50-75 words max. Beyond that, nobody in their right minds will read you.
Avoid heavy attachments, which take a lot of time to upload, but even worse, a lot of time for the recipient to download. If you are on a fast bandwidth environment, things will go quick on your side, but very very slow on the receiving end. People will have to wait for your cumbersome message to go through before they can access their important mail. They will hate you. Some may even decide to stop messages beyond a certain weight altogether, or filter out any messages from you after a few bad experiences.

When you send pictures as attachments, check out that they are sampled down in jpg format to at most 100kb before sending them out. (Click
here for more). Otherwise warn your recipients that something heavy is coming their way.