Some is generally used in affirmative sentences.
Any is generally used in negative sentences.
Any is generally used in questions.

This is true for something / anything, somewhere / anywhere, someone / anyone (or anybody / somebody) and even anytime / sometime (don't confuse with some time and any time)

However there are exceptions:

when the existence of the subject is not in doubt:
"Would you like some tea?" is fine because your host, hovering there with the teapot clearly has some available.

"Some" can be used in a negative to distinguish part of a group when "any" would imply the whole group:
"I like all brunettes but I don't like some blondes." is different from
"I like all brunettes but I don't like any blondes."
In the first case 50% (or so) are OK. In the second all blondes go unappreciated.

Also
"I'll find someone to help you." (implies that helpers exist.)
"I'll be grateful for anyone you find." (implies that helpers may not exist)

similarly compare:
"Sherlock is looking for something." and "Sherlock is looking for anything."

In this activity there are some examples which obey the usual rule. Most, however, do not. Some, arguably, might grammaticaly take both answers but the context should guide you to the more natural usage. The aim is to give you a "feel" for this curiously difficult usage.