As I went about my research, I found some great advice. When leaving offerings of food on your altar, rather than trying to “guesstimate” when the deity/otherworldly being in question are finished with your offerings, light a tealight candle and let them know that you will leave it there until the candle burns out. I typically do this in the evening and leave the offerings there until the next day.
With regard to what to offer, I was prompted to buy Baba Yaga a bar of red chili infused dark chocolate. European butter, maple syrup, butter tarts, chocolates, candy, and peanut butter pretzel nuts have also been well-received. I have a shot glass of alcohol on the altar at all times. Baba Yaga has shown a preference for Fireball Whiskey and green apple vodka.
This has been my experience and it by no means is a “rule”. I always recommend asking what the deity in question would prefer and following your intuition. You may have access to something they want that can't be found elsewhere, so it's good to keep that in mind.
