These are some broad ideas and comments on aspects of the UX design process and how to streamline and optimize your work. While I do consider this "best practice," these are essentially my opinions based on 20+ years implementing user-centric design practices.
The core of UX is the “experience.”
Work the mental model
What experience does it remind you of in the "real world?" What should it remind you of?
Tell the story
If you're not sure of the narrative of the UX then you need to think about the core story that you are trying to tell to you users.
Ask yourself “how does it feel?”
How does it feel; not just as an interface or an interaction but as a holistic experience.
A balanced approach to user-centric design.
Be a true advocate for the user
Regardless of other inputs, always stand up for the user and what they really need and want. Someone has to, and that someone is UX.
Balance business, tech, user needs
Be a user advocate, but seek balance with other inputs whenever possible; be a consensus builder (within reason) and work together.
UX comes first
Think about the user, think outside of the box, and think BIG before allowing technical constraints to limit your scope.
Don't skimp on discovery.
Don't rush designs
Take your time and conduct a robust discovery phase with research and testing before moving any pixels around.
Be quiet
When doing user research and testing, listen as much as possible without trying to inject opinions and hypothesis.
Validate ideas
There's nothing wrong with some early sketches, concepts, and hypothesis, but the goal should be to validate them.
The goal is to solve problems.
No design without a problem to solve
All UX design should begin with a goal in the form of a problem to solve; without this there's nothing to measure against.
Task-based design
Think about what users want to do and help them complete those tasks in the easiest and most intuitive way possible.
Less is more
Cut down required user tasks to the bare minimum and eliminate clutter that can potentially distract or confuse the user.
Know your users.
80/20 rule
Focus design solutions on the needs of 80% of your users who use a limited set of features; surface these features and hide everything else.
No "Stereotype" Personas
Group basic personas by User Types into categories according to what tasks they want to accomplish, and not by stereotyped personalities.
Design with artfulness
No matter how big or small, seek to create UX worthy of a museum shelf as this is something that all users will appreciate.
Embrace "living design."
There is no "finished"
Technology is always changing, and more importantly user behavior and trends mean that yesterday's "best practice" is today's "stale design."
Test, collect data, measure, iterate, repeat...
To ensure that the UX of a product is current, continuously monitor data via testing (qualitative) and analytics (quantitative).
Trends vs. Patterns
Try to monitor trends at least annually, and work to distinguish between what is trendy and what is an emerging pattern or best practice.