Make better use of the Dictionary
Every Mac OS X comes with several dictionaries. You can ofcourse open the app everytime you see an unknown word and look it up. But you can also do it quicker and faster.
Here’s how. Open the Dictionary application and go to preferences. Change the following setting as indicated on the image:

Now whenever you right click an image in Safari, Adium, Pages or whatever other application that supports it and select “Look up in dictionary” it should pop up a miniature menu like thingy that explains the word and offer some buttons to opt for more information.