You want to go after they have dropped their antlers and before the grass has really started growing again in the Spring since that will hide the sheds.
When they shed can vary depending on the area and the year,
One thing we do know is that after the rut, a buck’s testosterone levels begin to decrease, and when they drop to a certain level, antlers are shed. Since antlers shed at different times in certain areas and in certain years, something causes the testosterone levels to vary from area to area and winter to winter.
Source
Good places to look are usually wherever the deer are known to hangout during the time that they are losing their antlers. That includes places where deer go to scrape the velvet off their horns when the horns are growing, like aspen groves.
Snow will help, as long as the antlers are on top and not buried, at the same time sheds will eventually become bleached and then blend into the snow, while sticking out like a sore thumb in areas with dead/brown grass.
This is also a case where the early bird gets the worm, since other people will be looking for them, and animals will chew the sheds for the minerals.
