In most programming language modes, you can type C-M-i or
completion-at-point) to complete the symbol
at point. Some modes provide specialized completion for this command
tailored to the mode; for those that don't, if there is a tags table
loaded, this command can use it to generate completion candidates.
See Symbol Completion.
M-x list-tags reads the name of one of the files covered by the selected tags table, and displays a list of tags defined in that file. Do not include a directory as part of the file name unless the file name recorded in the tags table includes a directory. This command works only with the etags backend, and requires a tags table for the project to be available. See Tags Tables.
M-x next-file visits files covered by the selected tags table. The first time it is called, it visits the first file covered by the table. Each subsequent call visits the next covered file, unless a prefix argument is supplied, in which case it returns to the first file. This command requires a tags table to be selected.