Two weeks after your first usage?
No way. Even if you fully saturated your THC receptors that day I would still bet a good deal of money you would be fine.
I agree cranberry juice and things like that are in fact "poppycock"; the idea here is just to metabolize and sort of let the substance go through your body and be excreted. Things that encourage urination, sweating, etc assist this process.
Why do many people say it takes a minimum/average of 30 days to pass a urine test?
This is for people that have, for lack of a better word, established the metabolites in their system in a "deeper" manner -- they are much more saturated.
That didn't make much sense. Basically, if you smoke for your first time you'll probably pass within 3 days. If you smoke two days in a row you'll probably pass in a week. If you smoke every day for a month, you should probably wait a month before being tested. Get what I'm saying?
Being afraid about a drug tests two weeks after your first use..the odds are with you. Good luck.