It's always good to start with a compliment on what you like that they've done! From there.... just ask! If it's applicable to them, they're likely to respond. People who are obsessed with their craft, love talking to people about it.
This is gonna sound like a stupid answer, but honestly: just ask. People who are ahead of you have often been in your shoes, and even if they can't offer any tangible help, many will part with very good advice. The worst thing they can tell you is "no," so I say just go for it! I think you'll find that people are more generous than you expect.
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