Tuning Do's and Dont's

Aspect	Don't Be This Guy	Be This Guy
Limits	Don't start making changes to your tune without identifying your limits, both with the car and with your own background knowledge. Don't assume what the limits might be, even if you feel like you have an intuition based on a prior project.	Ask for help and identify what the limits are to the vehicle you're working with. Here are some examples: What timing advance is reasonable for your fuel? What boost pressure yields the greatest efficiency on this turbocharger? What boost pressure just "blows hot air"? Stick to your limits. Understand that if you don't know, it's better to stop and ask for information or help from our community before continuing.
Risks	Don't ignore risks or underestimate the possibilities for critical component damage (i.e. engine). Your risks are formed by your limits; don't fall into a false sense of security by disregarding limits. Don't make assumptions about your luck. Luck won't make your tune a reliable one.	Know your risks as you learn your limits. Here are some example questions to ask yourself: What are you risking by increasing the boost too much? What outcomes can you anticipate if you advance ignition timing too much? What are the possible risks of running to lean or rich? Realize that your risks are always present whether you want them to be or not, and physics doesn't care about your luck or your gut's feeling. Form a personal assessment. Compare it with your capabilities, both financially and your part reinstallation options. Can you afford to risk an engine? How much uncertainty in reliability are you willing to accept by inching closer or even past a limit? Be honest with your own risk assessment. Can you afford a new engine? If not, how are you going to approach tuning in a manner that reduces this risk? Are you and others who are ahead of you in the journey comfortable with your approach?
Goals	Don't be the tuner without a goal. Don't keep adding boost, timing, etc. just because it feels good and you're waiting to see if it'll be fast enough this time. Realize that not setting goals based on your limits is the fastest way to grenade your stuff, and you might end up looking back and wish you were more careful! As everyone always quotes, "my car felt the best it ever had before it threw a rod!".	Set your own goals. Have an end result in mind. Be realistic. Don't set unreasonable goals that are outside of your comfort zone. Derive your goals from your limits and your risk assessment. How close can you approach your limits, in contrast to the risk you're accepting in doing so? Stick to your goals. Don't "scope creep" unless you mentally revisit your limits and risks.
Learning	Don't blindly throw yourself at a problem and anticipate you'll learn-as-you-go. This is the easiest way to make big mistakes that you could end up regretting. Don't overestimate your own understanding. Don't forget that every platform is different, and a prior platform almost never affords you everything you need to learn about a new platform, even if you've tuned other platforms for a decade.	Don't set yourself up to learn things the hard way. This will be a lot easier to avoid if you set your limit, define your goals, and stick to them both. But recognize when something has gone wrong, and learn from your mistakes. Have some humility. Be open to other's advice. Be informed about your map changes; learn anything and everything you can before making, even seemingly small, adjustments. Understand what your map changes mean in the physical world. What is timing advance, really? What is the wastegate's job? How are these things controlled? Learn your sensors. What sensors does your vehicle provide? How do they work? What do the reported values mean? How and when can your sensors report values to you incorrectly? Learn and be comfortable with stock reported values. What does the OEM tune command? Why is it commanding it?
Process	Don't tune without a process in mind. Don't disregard your process and start trying random things if feedback from your car is suggesting your approach was wrong.	Making a change to your tune to realize one of your goals? Have a process. Get a second opinion on your approach to reach your goal or solve your problem. Is there a better way to dial in that wastegate map?
Data vs. Assumptions		Get comfortable reading and understanding data. Don't make assumptions about what is going on, get data for it. Even if your data is suggesting you are right about your intuition, don't fall victim to confirmation bias. Doubt your own preclusions unless you can verify them completely with reliable sensor data. Understand your knowns and unknowns: What do you know? This should be derived from your sensor data, not driver's seat feedback from the vehicle. What do you not know? These are called known-unknowns. This could be, for example, a possible condition that you don't have a sensor available to truly characterize, or even a parameter you have available, but didn't datalog in that last run. What could you theorize you might be missing altogether? These are your unknown-unknowns, or things that you don't know, that you don't know. A broader, deeper understanding of the physics involved helps eliminate these.
Patience		Be patient. Know what steps you'll take if your process doesn't work the way you expected it to. If you run out of ideas, and you're out on the street, will you be comfortable accepting that you need to do more research and head home, or will you get impatient and put your car at risk?