first you need a target.
go for the ones that reaveal alot in what they are wearing. like if you can see the boob cracks. then simply get some elevation on them. at school @ the top of the stairs i can look below everyone and they barely notice. once i saw some nipples
as for up skirts its the opposite. you need to get low.
next if you want a pic try to get a hidden camera. if my glasses were secretly cameras i would be so happy
be sure to add any useful sneaky ways to see the goods