Besides registers and markers (see @phils's answer about both and my other, [**Icicles**](http://www.emacswiki.org/Icicles) answer about markers), ***bookmarks***, particularly either autonamed or temporary bookmarks, can be helpful for this. You need library [**Bookmark+**](http://www.emacswiki.org/BookmarkPlus) for these special bookmark types.

* An [**autonamed** bookmark](http://www.emacswiki.org/BookmarkPlus#AutonamedBookmarks) is one that you do not need to name. It is quick to create and delete: just hit a key. The same key creates or deletes a bookmark at point. (By default, this is bound to `C-x p RET`, but you can of course use any key.)

* Autonamed bookmarks are, like bookmarks in general, persistent. But you can optionally have them be deleted automatically.

* You can also create [**temporary** bookmarks](http://www.emacswiki.org/BookmarkPlus#TemporaryBookmarks) or make any existing bookmarks temporary. You can, for example, choose to make autonamed bookmarks be temporary automatically.

* You can quickly [cycle](http://www.emacswiki.org/BookmarkPlus#CyclingDynamicSetsOfBookmarks) among a given set of bookmarks. For example, to cycle among autonamed bookmarks, use commands `bmkp-next-autonamed-bookmark-repeat` and `bmkp-previous-autonamed-bookmark-repeat` (binding them to keys).

* You can [highlight bookmarked locations](http://www.emacswiki.org/BookmarkPlus#HighlightingBookmarkLocations) in different ways, so it is easy to spot them.