The main options are interleaved posting (also called inline replying, in which the different parts of the reply follow the relevant parts of the original post), bottom-posting (in which the reply follows the quote) or top-posting (in which the reply precedes the quoted original message).

Instead of top posting, we should be replying inline—that is, from within the body of the original email message. In Outlook and Apple Mail, you can see the original message as soon as you hit reply.

Inline posting allows people to easily read your reply and the content being replied to, even if they haven't seen the original message. For this reason, it is the standard quoting style for public forums on the Internet. Here is an example of inline quoting.

In the more general case, there are several points being replied to and the replies are interspersed, so that "interleaved posting" (or "interleaved quoting") is a more appropriate term. I still use "bottom posting", however, in symmetry to the opposing style of "top posting".