Before indexing the phrases in the phrases buffer, they should be
checked carefully for consistency. A first step is to sort the phrases
alphabetically; this is done with the command C-c C-s
(reftex-index-sort-phrases). It will sort all phrases in the
buffer alphabetically by search phrase. If you want to group certain
phrases and only sort within the groups, insert empty lines between the
groups. Sorting will only change the sequence of phrases within each
group (see the variable reftex-index-phrases-sort-in-blocks).
A useful command is C-c C-i (reftex-index-phrases-info)
which lists information about the phrase at point, including an example
of how the index entry will look like and the number of expected matches
in the document.
Another important check is to find out if there are double or
overlapping entries in the buffer. For example if you are first
searching and indexing ‘Mars’ and then ‘Planet Mars’, the
second phrase will not match because of the index macro inserted before
‘Mars’ earlier. The command C-c C-t
(reftex-index-find-next-conflict-phrase) finds the next phrase in
the buffer which is either duplicate or a subphrase of another phrase.
In order to check the whole buffer like this, start at the beginning and
execute this command repeatedly.