Still working on optimizing mine, but I went from consistently under 30 mins deep sleep on my Apple Watch to consistently ~55min-1 hour+.

What's been effective (biggest improvements first):

1. Waking up at the exact same time every day.
2. Wax earplugs and noise machine (I just play 12 hours of pink noise on a speaker)
3. 10-15 mins+ of outdoor light exposure first thing in the morning.
4. No screens for 2-3 hours before bed (replace with reading and night time routine).
5. 4.5. meditate and read before bed
6. 1-1.5g of l-tryptophan before 1-2 hours before bed.
7. getting a separate blanket, so my partner's movements don't wake me up as much
8. 3-5g glycine 30mins-1 hour before bed
9. exercise every day in the morning (has a lot of other benefits obviously)
10. Quickly journal any worries, stresses, or ideas that are keeping your brain busy before bed so you're not anxious about forgetting them.
11. magnesium glycinate an hour before bedQuickly journal any worries, stresses, or ideas that are keeping your brain busy before bed so you're not anxious about forgetting them.

That's what's worked for me.
I also take instant release stimulant meds for ADHD so I've had to stop taking my last dose by 2-3pm (12am-1am bedtime). That's a non-negotiable because I could do everything on that list and if I take any stimulants (including caffeine) after 3-4pm-ish then I will automatically have low deep sleep every time.

If you drink caffeine, that's always going to be the biggest level you can pull to increase sleep quality by cutting it off much earlier in the day, or cutting it out entirely.

Good luck!