Your main focus should be on the semantic history of the word, but you may also devote a section to its formal history, including the sound changes it has undergone.
Thus you want to start with a single word which has developed several meanings.
Do not combine two or more words which are historically unrelated but happen to have the same form, such as bear (animal) and bear.
You should deal primarily with the history of the word from the time it first appears in English. You will not have as much information on either meaning or form for its pre-English history.
You do not have to deal with every single meaning the word has ever had, but it would be good to try to cover the main meanings that are still in use. You might look the word up in a very small modern dictionary, to find what are the most common meanings in modern English.
Focus on each new meaning as it appears, and see if you can classify the change according to the various types discussed by Crowley and in the lectures. If you are discussing sound changes, see if you can identify them similarly.
Your major source of information will will be the Oxford English Dictionary (OED), Online version, or hard copy (2nd edition) in the library. Any other sources you use should be listed as references in the normal way.
OED has an abundance of quotations illustrating various meanings of the word at different historical periods. Please resist the temptation to quote dozens of these -- use them judiciously.
Among the words that students have written on in recent years are:
Bar board bureau carry case cell common cool copy craft crook cross culture dear dog draw earth element fast fire foot form game general gossip hack hand head history house icon idea light march match meat nature nice one pass patch pinch pitch post pretty quick run science sentence sign single society soul stage stock study summer story stuff tack trail vision wild
If you are wondering how one could write a history of a word, you might find it interesting to browse in Keywords: A Vocabulary of Culture and Society, by Raymond Williams, which contains historical studies of many words of cultural, social and political significance. An e-book version is accessible through Voyager.