Best practices are starting points: if you have no data, start with these. They are not what you should end up with, but it’s where you start (the optimization). That’s an important distinction.
Here are some ideas about of how you can apply 10 Jakob Nielsen Usability Heuristics to lead generation websites in the B2B or high consideration B2C realm, where there isn’t necessarily any transactional functionality, e.g. e-commerce, user registrations, etc.