My goal is to get to Hawaii post Career Course. That's 2-3 years away so it's a ways off, but I'm a planner. I know that assignment is wanted by everybody in the Army and it can be a crap shoot to get.
First of all, there's nothing you can do. Assignments post-Career Course are given to each class on a needs-of-the-Army basis. For example, my class had 1 Germany slot, 1 Hawaii slot, a couple to Korea, like 12 to Fort Hood, etc. If your class hits the timing wrong there may be no slots for Hawaii and there's nothing you can do about it.
Second of all, just be professional when you talk to him/her. They're customer service and they know it. It's their job to balance your desires/needs with the needs of the Army. At the end of the day it's going to come down to what the Army needs and trying to find something you want that fits or comes close to fitting that need.
Be wary of the short tour thing. It can usually work out to get an assignment of choice but I've heard numerous stories of people volunteering for a deployment or a Korea tour to get what they want afterward, something coming up in the world, the needs of the Army changing and then they don't get what they want.
Just be flexible and make the most of any assignment you get. My next assignment is the first one I've ever got that I WANTED. However, every job I've had (with the exception of an XO in TRADOC as a first job in the Army) was the perfect job for me at the time, I learned a lot from, performed well, and went on to the next bigger and better thing.
This is true! The best thing I found out as a recent graduate from my CCC is to attend as a "senior" CPT aka KD-complete. Your assignment list will be different from that of everyone else who does not fall under that category and the opportunities are plenty. This is true given the amount of CPTs/1LTs who for one reason or another are rushed to CCC only to find themselves competing with a much larger pool for those desired assignments. I am one of the few that was KD-complete upon attending CCC and assignments in Germany, Hawaii, Netherlands, ROTC, and recruiting were only a few of the great opportunities available. If the opportunity presents itself to delay CCC for a KD position, take it! Now I understand more and more CDRs are looking for CCC as a requirement for Co CMD, but if your branch treats any other assignment as KD, don't hesitate to run with it.
Also, do not be too concerned about building a relationship with a branch manager right now. That person may or may not be in that position when you need them as those are on rotational basis as well! Concern yourself more with maintaining your ORB and OMPF up to date & that they match. You never know when HRC is looking at your file for some key assignment and don't even know you were passed up on it. Best of luck to you!