- Don't use pesticides
- Reduce or eliminate outdoor lighting
- Create habitat
1 is a no-brainer.
2: Artificial lighting will confuse lightning bugs or prevent them from mating, since females need to see that fancy swoopy-light dance to find a mate. When they don't mate, you lose out on the next generation.
3: I've had success in my yard because I've carved garden beds out in my lawn where I've planted a lot of different native plants, and I try to only minimally disturb the beds throughout the year, so lightning bug larvae have free reign in the leaf litter in fall and winter