One technique I've found useful for self-reflection is to make a list of questions to answer periodically. Start with a few important questions the answers to which will reveal something about who you are and who you want to become. Here are a few questions from my list (obviously you should feel free to make your own list):
- Rank the following in descending order of importance: accomplishment, career, family, friends, happiness, health, joy, love, meaning, pleasure, religion, status, truth, wealth.
- What's the smallest amount of money you would accept to be instantly fast-forwarded one year of your life?
- By your estimation, what's the percent chance that our universe was created by an intelligent entity?
- How many people are there in your life who would be willing to use up a vacation day to help you move? How many people would you be willing to do this for?
- In the last month, what percent of the time would you say you were happy?
- What do you plan to accomplish in the coming month/quarter/year? What will you do to make these things happen?
- What do you regret about your actions/behavior from the last month/quarter/year? What do you want to do differently going forward?
I suggest setting a specific schedule (for example, answering the questions on the first of every month or every quarter). Although the specific answers you give each time will tell you a lot, you'll probably learn even more about yourself as you look back at your earlier answers and see how they've changed over time, so don't look at any of your earlier answers until after several iterations.
Also, if there's someone you want to understand better (and are prepared for differences of opinion), have them do the same, and both guess what the other's answers will be, then discuss any surprises.