There are no complimentary upgrades on HNL-GUM unless a cabin is oversold, in which case they would upgrade passengers to the next cabin in order of status. You can upgrade with miles; for upgrades to business class, there's a co-pay that gets refunded if the upgrade doesn't clear (upgrades are often waitlisted). Upgrades to Premium Plus have no co-pay. The upgrade waitlist is also prioritized by status, and you can be jumped on the list by someone with higher status even if they book after you do.

Your other option is to look for a discounted cash upgrade offer, which you may see at any time from booking to check-in. Note the terms of the offer carefully -- generally, if you make a voluntary change to an upgraded itinerary, the upgrade fee may be forfeit.

The days of "scoring upgrades" by dressing nicely, asking at the check-in counter, etc. are long gone. The airlines have monetized the system.