What advice do you have for someone trying to switch from active duty Navy to Select Reserves?

Learn how the reserve side counts time so you don't lose a "good year". Your "anniversary year" starts the day after you leave AD and you need to get the requisite number of inactive drills in prior to that date next year. So when dealing with the reserve recruiter, make sure you lock in the billet you're going to so you start right away. Also you really need to make sure you're DD214 is accurate and get anything corrected prior to punching out. Make a copy of your medical record because things get "lost" sometimes.

Check with the local NAVRES recruiter and verify your rate is open in the reserves as a lot of time they're not

You will need to speak with your retention NCO or possibly a recruiter.