1. Literature Search Perform a thorough literature review, even if it means having to understand several different areas. You don't want to find out after 4-5 years of hard work that your dissertation work has already been done. Also, performing a thorough literature review will give you an opportunity to leverage existing work, so you don't have to start from scratch.

2. Four key questions For every research investigation (along the way to completing your dissertation), be able to concisely describe:  1) what is the problem you're addressing (also why?)  2) what is your hypothesis?  3) what is the scope of your proposed solution?  4) how will you validate the solution?

3. Never stop writing Be sure to write up your research results as you go along. DO NOT wait until the end of your dissertation to publish papers about your work. You need to get feedback from the community as you go along. The other side effect is that it will be much easier to compile your dissertation.