I go with the following approach every time I see the New Player notification at the beginning of DF content.
If the person says "Hi, first time here, I need advise." - the door is open for any explanation, mechanics or skills.
If the person says "Hi, first time here." - the door is open for any mechanics explanation.
If the person says "Hi" or nothing - the door is closed until we wipe. Or, that player repeatedly dies to a mechanic.