Distinguish between main titles (<TITLEPART TYPE="main">) and subtitles (<TITLEPART TYPE="sub">). Statements of responsibility ("by H.W.Smith") should be in <BYLINE> tags, with the author tagged as <DOCAUTHOR> (but nothing else belongs in the byline).
Record line breaks within tags on the title page by use of the <LB> tag. Title pages are one of the few places where we preserve such formatting. Don't worry about recording line breaks between tags (say, between the byline and the docimprint).
If there is more than one title page, place each in a separate <TITLEPAGE> tag. If one is a "half title", give it a TYPE attribute of "half".
Record both the front and the back of the title page, with a <PB> tag dividing them. If the back of the title page isn't numbered, use <PB N="verso">. If the title page itself isn't numbered, as it usually isn't, use <PB> without any "N" value.
Material that doesn't fit properly in any of the other tags, e.g. declarations of copyright registration, can be placed in <DOCIMPRINT> tags (this is the one that we've chosen to "abuse").
Here's a sample of a simple one:
<TITLEPAGE><PB>
<DOCTITLE>
<TITLEPART TYPE="main">The<LB>Two Philosophers</TITLEPART>
<TITLEPART TYPE="sub">A quaint sad<LB>Comedy</TITLEPART>
</DOCTITLE>
<BYLINE>By <DOCAUTHOR>J. J. Chapman, Ll.D.</DOCAUTHOR></BYLINE>
<DOCIMPRINT>
<PUBPLACE>Boston</PUBPLACE>
<PUBLISHER>J. G. Cupples Co</PUBLISHER>
<DOCDATE>1893.</DOCDATE>
</DOCIMPRINT>
<DOCIMPRINT><PB N="verso">COPYRIGHT, 1892,<LB>BY J. G. CUPPLES COMPANY.<LB>
<HI REND="i">All Rights Reserved.</HI>
</DOCIMPRINT>
</TITLEPAGE>