The best and only thing that you can do now to become an attractive candidate for a position as a flight paramedic is......drum roll, please......become the best ground paramedic you can be.
Work for a progressive 911 system. Learn to be calm, respectful of everyone around, and methodical, even on the most hectic scenes and with the sickest patients. Read journals, blogs, and websites. Look things up online and in textbooks. Don't be afraid to say "I don't know". Don't be cocky or a know-it-all. Take classes that you think will help you understand and do your job better. Precept. Teach, both informally and maybe formally. Earn a 4-year degree. In a couple of years, go to work for a ground CCT service and then start this whole process over. Become the type of paramedic that other EMT's and medics love to have as a partner, that docs and nurses and firefighters and cops like to see walk through the door, and that people say about "if my wife or kid ever gets badly hurt, I hope cointosser13 gets the dispatch".....not because you know everything but because you just always do a really_good_job. That should keep you busy for 5-6 years......after you've done all that, start seriously looking into flying. But don't do these things because you think they will help you get into flying, do them so that you can get really good at what you are doing now.
HEMS programs typically look for paramedics with quality experience, who are mature as both an individual and as a clinician, who are easy to get along with, who are confident but not cocky, and who have really good customer service skills and crisis-management skills. They'll figure this out through interviews, scenarios, testing, and talking to people who know you. Some people naturally possess these "soft skills", some don't - but they are critically important - you will NOT get hired by a good program if they don't get the right impression of your personality, no matter how bad*** of a paramedic you are or how many critical care courses you've taken or how much physiology you can rattle off. Reputation is important. Many programs only hire people they know, or at least people that they know have a good reputation in their area.
Don't spend the next few years of your life focusing on becoming a flight paramedic and just checking off the boxes that you think will help you reach that end. Nothing wrong with having a goal and a plan to get there, but enjoy what you are doing now and work hard to be really good at it.