Make sure that the information you enter is accurate, and not a technique that happened to work in you circumstance.
Do not remove any steps that are valid but failed in your circumstance. Explain in a sub step of the failed step your problem and the solution you found to this failure.
If the HowTo is accurate but for an antiquated topic. Recreate the old HowTo with a more accurate, descriptive title. Create a new HowTo with a descriptive title. Link the older HowTo from the new HowTo.
If the existing Howto has a similar name, but unrelated subject, move the page to a more descriptive name, create the new page under a more descriptive name, and create a disambigious page linking both.