This section can be subcategorised into reverting a change to text, and reverting a change to an image.
Whilst SysOps can revert the edit of a user with a single click, other editors must manually change adjustments to articles. The level of difficulty an editor faces when trying to revert a text edit usually depends on the circumstance. Some reverts are easily done, such as simply removing a comment made previously. However, more complicated revert is trying to restore deleted text, or go back to how a page was originally written. In order to do this, one should click on the article "history" at the top of the page, and click on the time/date that coincides with each revision ever made. You should then click "edit". There will be a warning at the top of the page highlighting that you are editing an out of date version of the article. By ignoring this and simply clicking "save page", the article will revert back to the revision you accessed.
Please note, when carrying out a revert it is encouraged to, for instance, write in the summary box "reverting edit" just to show clearly your actions, particularly for reference purposes on the history archives.
Reverting an image change is actually much more simple than many users think. Click the image you wish to change, and the history should show itself below on the new image page. Similar to a text revert, one should find the appropriate revision, and next to it click "rev". This reverts the image to that revision.
Please note, however, that an image revision can take a few minutes to take effect. Also, your browser cache can sometimes save the image the first time you access it. Thus, even when you've changed the image the old "bad" one will still be visible. Usually though after a few minutes, your computer catches up to the changes made.
For more specific advice on reverting vandalism, see Lostpedia:Vandalism