If going along the on-ramp behind a car, leave enough space between it and you so you can speed up to merge into the freeway traffic. If you are right on his bumper the only option you have to change speed is to slow down. You want to be able to do either to move into the travel lane traffic.
Plus, you have got to take your eyes off the vehicle ahead of you while merging so you can do a head turn and check your mirror. If the guy in front slows abruptly while you're not looking, that's bad.
While on any multi-lane highway, never hang out in someone's blind spot. Move on through it or slow a bit to let them get ahead.
While in the right lane, watch for vehicles merging with your lane. Although they are supposed to match speeds with the traffic, don't count on it. I will adjust mine so if they merge abruptly I am not nailed. The cemeteries are full of people who had the right-of-way.
Run with your high beams on so you are slightly more visible in someone's mirror or if they do a quick glance before a lane change. Do not be hesitant about using your horn to let them know you are there.
I wear a high-viz yellow mesh vest over my textile riding jacket. Makes me much more visible.
Don not focus only on the vehicle in front. Watch several vehicles ahead. That save my butt on I-40 when I noticed the line of cars jinking to the right side of our lane. There was a large truck retread casing in the left of our lane and with that extra warning I missed it easily without having to make an emergency dodge.
And maintain good following distance. At those speeds you need it more than at 45 mph. If someone pulls into it, and they will, just open it up again. Tailgating at 70+ mph is very hazardous.
Keep an especially sharp watch for out of state plates when nearing an interchange as they are on unfamiliar roads and might make a kamikaze dive across lanes to exit.
Actually, always be wary when nearing an off-ramp. I commute on part of I-40 and see many drivers speeding past me in the left lanes only to dart across two or more lanes to dive towards an exit.
And watch for any type of rental truck or trailer, e.g. U-Haul, Ryder, Penske, etc. That large truck or combo is likely being driven or pulled by someone who normally drives a compact car. They are not used to using mirrors and have no idea how long that thing is when changing lanes.
If you have to ride next to someone, do it even with the driver's window so they see you.
And +1 own the Sunday morning rides for quieter traffic. Good luck.