Welcome, i'm new to this hobby, i started to collect chips this year, so i have not too much experience. But i will to share mine.
I was in Vegas in March and i harvested a good amount of chips. I simply walked at the cashier and ask if they had any uncirculated or almost new chip, in almost every casino i found something. Sometimes they have not really good chips, or maybe they don't have time to check for you. In this case try to walk around tables, to see if there's any dealer alone and try to ask him. It's better to wait when there's no people, this is true when you go to the cages too, if cashiers have nothing to do you dont made people waiting to change angry and they seems to be more helpful. Best time is late night or early morning. Usually if the person doing the search lose some time, walking on the back of the office, asking other co-workers if they have some, i left a tip, one or two bucks, it's up to how i was happy for the amount of chips found and the time spent. In this way i took a good amount of new chips.
Dont forget to get some traders, if you find something really new it's always worth to buy some extra (this is was some collector said to me, and i agree).