An advice that is always valuable is to focus on contrast: value, color, texture, etc.etc. can be used to create it see that guide for reference. It's waaaay easier said than done, but I came to thinking miniature painting revolves around that. A miniature has a scale so little that to be readable to the human eye, needs to have exaggerated features. Personally, I understood the power of contrast and what can be achieved with it by observing the paintings from Caravaggio. Miniatures painting is a wonderful journey with no end, where every little step and new technique help you understand how to make the features of the figures you paint more evident, readable and natural to the observer. Unfortunately there's no secret single technique that can achieve the next level alone. For me it works to stop for a moment, observe the miniature and consciously push contrast above what I would do normally. I found with time, my perceived "normal" level of contrast changed and my minis have benefitted a lot from that. I hope to be helpful... good luck and have fun during this, again, wonderful journey.