Is there a computer program or internet site that I can go to which can analyse a piece of text and tell me how often a particular word appears? I'm thinking of something along the lines or a feature that will tell me which words I use most frequently in a piece of writing.
Word will do it for you. Press CTRL + F for the find function, enter your word, tick the Highlight All button and click Find All. It will tell you how many it found.