I lived in Long Beach just a few years ago. I also researched the heck out of the place before moving there, since I'm pretty picky about my neighborhoods, so I know quite a lot (both good and bad) about the various neighborhoods and areas of town. If you have any specific questions please feel free to PM me!
In terms of general recommendations, as mentioned above, the port and the Queen Mary are both pretty cool. There are also some great museums in town - art, science, history - if those might be your jam.
My personal favorite site was always the Skinny House
, but that's me.
As for restaurants, if you're at all interested in Thai food - and non-chain, unique local places - definitely check out Thiptara
. I now live further south and I still make the drive to LB solely for this place. Incredibly clean, delicious food, spacious and friendly restaurant (albeit with a small parking lot that's tricky to get into).
Happy to help more if you need it - just let me know!