And here are some good pieces of advice from the Internet:
Here are some criteria to keep in mind when choosing a dissertation or thesis topic.
1. Choose a topic you love. This may be the most important criteria. You're going to be spending so much time with this project, and your quality of life will be much better if these hours are spent enjoyably. What's more, the quality of your research, writing, and arguments will be much better if you feel genuine passion for your work, Choose a topic you find both fascinating and socially significant. Never let someone pressure you into writing about a certain topic!
2. Pick something your advisor finds interesting and is knowledgeable about. Of course, is this is not possible, you might want to change your advisor instead of changing your topic.
3. Pick a topic that will be helpful in your career path. If your goal is an academic career, pick a topic that you can easily modify into journal articles or a book, and that will lend itself well to future research. If you want to work at a teaching oriented institution, consider a topic you can use in the classroom. If you are going into industry, choose a topic that will make you more marketable.
4. Find a topic that establishes your niche in your field. Do your research and find a topic that fits into existing bodies of literature, but that builds upon theory and expands it.
5. Choose research that is unique. Do significant research to make sure this topic has not been done before. Be creative and choose an idea that stands out from the pack as original and innovative.
6. Think carefully before you choose a controversial topic. Academics are a sensitive lot, and in every field there are certain topics and positions that will send highly educated people into intellectual temper tantrums. This doesn't mean you should avoid topics that push people's buttons. However, if you choose a controversial topic, think carefully about whether it might restrict your employment, tenure, or publishing opportunities.
7. Pick a topic that you already have some expertise about. This will help preserve your sanity and get you out the door faster. This isn't the time to explore a brand new area. Along the way, take coursework and write class papers that will help you write your dissertation or thesis.
8. Pick a manageable topic. This is a huge project, but it isn't your life's research. A good advisor will help you narrow down your topic so that you don't remain in graduate school for many long years.
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