Exchange rates will always change (usually not a lot, but keep checking for good deals)

Almost every exchange location charges a fee and may charge you by amount 

• I went to Territorial Savings Bank and they charge a flat rate fee of $5 per transaction

• Call first to see if they have HK dollar in stock, because I had to order mine.  It normally takes about five business days to receive, so make sure you give yourself time.  In my case, I ordered my money on Thursday and it was already ready to be picked up on Monday. 

Bring cash, because most places charge extra if you use credit

Think about whether or not you want to open a bank account in Hong Kong, so you know how much money you plan on exchanging before you leave