I had one of these in September for legal reasons.
I lied a ton.
Basically say you rarely drink, when you do drink you only have 3-4 beers over like 4 hours. Say you never get out of control with alcohol. Also, say you have never blacked out, and always remember everything. Obviously don't just straight up say this answer their questions.
As to weed I would just say you have smoked a few times but don't enjoy it because you get sleepy.
I had to have someone who knew my drug use call the councilor that evaluated me. I just had a good homie call and told him what to say ahead a time and everything went well.
Good luck.