OK so security clearance.
The Australian Government Security Vetting Agency
these are the guys I work with as I'm the security Manager at our site.\
we have staff go though Neg 1 vetting,.
they check:
full family esp if any over seas, so parents siblings etc
full finance, all loans, debts, income, strange expenses etc
travel for the past 10 years..(i'm redoing mine atm, and with 50-100 OS trips such a pain)
all places you have lived in past 10 years
school/uni grades
they will contact ex teachers friends etc to get a feel for your charature
questiosn about drug actions
partners and such will get a mild BG check.
then there 2 levels of security higher.
so similar info just for longer and more back ground
all I can say is be honest.
if you smoked dope for a couple years admit to it, as if they find out you lie it worse than saying you did it.
that said better if you didn't
multiple speeding fines not so good.
multiple drink driving will fail you
any criminal conviction is very bad.
if you need more info PM me and I can give you a call and discuss.