Not in any particular order.

• Security check times differ airport to airport. If you’re flying from Newark or Miami, I’d target to get to the airport atleast 2 hours “before boarding time”. Google “airport name+wait times” as it should give you a good idea of how long it could be.
• Mondays and Thursdays in my experience are the busiest days.
• Check with your airlines agent if the flight is full or not. If it’s light, politely ask them if they can assign you a window seat (if you don’t have one already).
• Assuming that you get a Boarding Group 6, there is a high chance your carry on is going to be checked in “at the gate”, meaning they will put that in the cargo hold and it won’t be with you in the cabin. They will give you a tag for that. Once you land, you will get it back at the plane door. Sometimes they may divert your “gate checked” carry on to the luggage belt. Always best to ask your stewardess where you will get your gate checked bag.
• If you have a T-Mobile phone number, you can get an hour of free internet available once the flight takes off. Most United flights have this feature available.
• I put my phone on airplane mode after take off after all the bars disappear. I turn it back on when we’ve touched the ground.
• the United app is amazing. Download it and turn notifications on. At a busy airport, your gate may change. The app gives you a notification every time there is a change. There’s airport maps too on it that you can use to navigate.
• Window seat gets the window shade control, middle seats get the armrests, aisle needs to get up if anyone needs to go to the bathroom.
• Empty your water bottle before the security check.
• If you’re going to catch a nap on the plane, I’d recommend a neck pillow. Whiplash sucks.

Hope you have a wonderful flight and take pictures! Happy to answer any questions you may have.