Forcing and preventing page-turns

[David Sumbler]

It always seems to be a bit hit-and-miss for me when I try to arrange
the pagination of instrumental parts.  Reading the manual it isn't
clear to me how I can force page turns to occur *only* at the points I
choose.

Also, Lilypond doesn't like ending on an even-numbered page.  How can I
force it not to add an unnecessary extra page at the end of a part?
 The reason is that the part in question can fit on to 12 pages.  I
don't want it extended to 13 because that means an extra sheet of paper
and 3 blank pages at the end of the part.

David