Guard Units tend to be a tight knit group. Unlike the active duty side, you don't have guys transferring in and out all the time. They need to know that you will fit in with the bro's and will be there for the long haul. If you are a hometown kid, then that is a huge benefit. Your civilian flight time is another benefit. As far as the interview goes, good advice is listed above. Clean cut, conservative suit, no funky ties, etc. DO NOT under any circumstances come off like they owe you the job. What they want to know is that you have a proven track record of hard work and discipline. Good grades in school etc. They need to know that you will be disciplined and mature enough to make it through pilot training. If you didn't have good grades (like my 2.6 in Business) focus on the fact that you worked 40+ hours/week to pay for school, or for flying lessons or whatever. I don't know your exact situation, but lay it out like you had a goal, you set a plan, your worked your butt off, and you achieved it. For example, did well in high school, got a degree from BFU with a 2.1 in basket weaving. I would have liked to have done better, loved the subject and studied hard, but I was busy working two jobs to pay for school AND flying lessons. Now I am back home, building flight time, and working as a flight instructor which is what I have planned to do since I was 8.
Last bit of advice. Don't talk too much. If you are a geek for weapons or airplane trivia, don't ask questions to show them how much you know. Let them show you around, find out about you. Questions I would ask them:
Amount of time that they deploy and where.
Time that you would be on active duty, can you stay active longer if you want?
What's their qualification progression (2 ship lead, 4 ship lead, ip etc)
Ground Jobs/responsibilities within the squadron.
Best of luck! Keep us posted.
BobbyB