From what I've noticed the incenses, incense seems to help a little, and the lure module seems to help some. It seems like the more heavily developed areas of a city have good spawn rates. I
I agree with previous answer, it does seem like cellular activity makes a big difference. It seems like the more heavily developed areas of a city have good spawn rates. Also if u are in downtown or on outskirts. TheThe less there is in the area, the less pokemonPokemon seem to spawn.