G'day siberia-man,

There's a lot of good advice already. Here's some additional information, which I didn't see posted, and mostly reflects my usage (garnered over the last decade).

The <pre> tag is useful when the content contains non-ASCII characters which may be rendered as character references when <code> tags are used. For in-line, as opposed to block, content I use the <tt> tag. Everything already said about <pre> (e.g. escaping characters) also applies to <tt>. Compare these smilies: &#9786; and ☺ (the 1st uses <c>; the 2nd uses <tt>).
[Note: Rendering of non-ASCII characters may be dependent on various things such as browser capabilities and available fonts.]

Be aware that <code> tags wrap lines (the 2nd and subsequent parts are introduced with a +); however, <pre> tags won't do this. Keep an eye on the length of lines in <pre> blocks; and bear in mind that indentation from "Re:", "Re^2:", ..., "Re^N:" posts will affect wrapping.

You can nest <c> inside <code> and vice versa. The two pieces of markup I used there were: <code><c></code> and <c><code></c>.

You can enter [ and ] using &#91; and &#93;, respectively; e.g. [not a link] which I marked up as just "&#91;not a link&#93;" (i.e. no tags needed here).