Tonight I'm going to show you step by step how to revert an edit. Some of the steps can look intimidating to newer editors but never fear I'm going to use pictures so you can see how its done, then turn you loose to clean up the crap.
Firstly it is really important to understand Watchlists. Here are two blogs I've written about the topic.
Very Very Basic Editing
Watchlists Again Busy Busy Me
Adding pages to your watchlist is the first step towards reverting vandalism. You can only revert edits if you are made aware there is a problem with the page. In order to do that you have to have a watchlist. Adding pages to your watchlist is fairly simple. First you need to be logged into Wikipedia. Then every page that you think you might be interested in watching you need to actually go to. You will see an empty star on the right side of the page.
Click on the empty star and it will turn blue and give you a message that you have just added this page to your watch list. Click on the blue star and it will remove it from your watchlist. Okay?
Here is what the right top page looks like for me.
Click on the "my watchlist" and you will see every page that has been changed appear on a daily list. Here is a snapshot of what I'm looking at.
The lower case "m" means that it is a "minor edit". You can remove all the minor edits from the watchlist cue. I don't want that option because the person who is making the edit selects "minor edit" before saving. I'm suspicious that someone trying to sneak through vandalism will check the minor edit box so that very few people notice.
Also whenever someone edits a page they give a reason why they edited it. Sometimes it is simple like "typo" or "added reference" something simple that you might not even check. Again what is written in that reason box was written by someone who might be wanting to sneak something in.
So I check everything on my watchlist, even if it looks innocent. Another reason I do this is that I can learn from the better editors.
The color + and - numbers in the ( ) I believe mean how many characters were added or removed. That's another clue to whether you should check the edit or not.
On the left side it says "diff" that means the difference before/after.
I'm trying to find some vandalism, but of course I can't find any at the moment. Here is an edit I made a couple days ago for Mark Edward's page. It shows up like this on my watchlist.
When you click on the "diff" you will see the page I linked to below.
Mark Edward WP page with slight change
The right side is yellow and the left side is green. Every change is in red print. So you can see I changed the word "a" to "as"
On the top right side above all the green you will see this area.
See the "undo" box. If you click that you will see the following...
Scary message telling you that if it is vandalism you are reverting you don't have to leave a reason for the revert. If not, then you must explain why you are reverting.
Personally I like to leave a reason that might help the editor. If it is something that I can't sum up in a few words then I will go to the discussion page and leave a more detailed reason why I reverted their edit.
Near the bottom you will see this area...
See where you can click the "minor edit" box? You write in the area that starts out with "undid revision 466...." the reason why you are reverting the edit. Then click "show preview" to make sure you did it correct. Then "save page".
Okay, now your free to help keep Wikipedia vandalism free.