I just completed my second shift off orientation, with about a year of tele experience, so my advice is framed from that perspective.
For factual stuff, the ICU book by Merino, as well as CCRN review materials are often suggested. Most hospitals have fairly extensive education programs, my surgical/trauma icu actually hands out a 4 inch binder on day one of things to know/learn.
For actually getting through your day, it seems to help to communicate how much respect you have for your co-workers and their abilities. This seems to play largely as they take time to explain/show/do things for you. For example, now that a preceptor is no longer paid to be with me if I have to have someone draw blood on one of my patients I attempt it a couple times, then assemble all of the supplies a coworker needs and have them ready so the coworker can come in, do it, and go on their way. (they often encourage me that with practice I will get better before they leave my room).
From what I can see of my co-workers so far, being a "good" ICU nurse is a 50/50 mix of factual/experiential knowledge and socialization/communication.
If someone has told you something (how to do a procedure, a factoid) and someone else tells you the same thing, if you tell the second person that you already know how to do something, it can be received not so well. This can be an awkward balance of not having someone waste their breath vs. attempting to be grateful for them taking time out of their day to teach vs. communicating what you do really know.
Overall try to study hard facts when you are able, ask pertinent questions, and be genuinely grateful for the help of others. If by chance you have spare time at work, ask people if they have anything cool or sick going on. Most people like to take on a teaching role. If by chance you have free time at work go around and see if you can help someone who looks really busy (even vitals/turns etc.)
You probably wont feel completely ready to come of orientation, no matter how long it is. At least this is from my personal experience as I was about to ask one of my managers for additional orientation and she informed me that she would be scared if someone felt completely ready to be autonomous.
But, like I said, I just got done with day two...