With character representations, the DVDs/Blu-ray or whatever the format the TV show comes in is the best way to figure out the behavior of the role in question. For me, it's JAG, so I expended the money to buy ALL the JAG episodes on DVD to make sure that I didn't stray too far off canon.
With some military items depending on the scene, I find that nothing replaces being able to feel the item in question in your hand, to feel the weight. I've taken a gun safety course (even though I never bothered getting out my firearms license) just so that I knew how to handle a firearm, both restricted and non-restricted (in Canada). I bought a set of USN CNT khakis just so that I could describe the feel of the fabric on the skin of the character as he walks towards a certain location through the bush...or know whether khakis would catch on a branch and pull on the thread. I've bought BDUs just so that I could get a sense of the tactile reaction of my fingers running across the fabric and I bought insignia in various sizes to get a tactile feel of what their shapes are like, how they'd fit in the palm of one's hand, whether the points protected by the clasp would indent the fingers as the hands closed around them. I've held Airsoft M-16A2s to get a feel of how the rifle feels while holding it (though not the exact weight, the shape is pretty close) I have a metal Beretta replica that comes pretty close to the weight of the real Beretta just so that I could feel how the clip drops into my hand as I go for the next clip and timed it to see just how fast I can drop a clip and replace it to see if a scenario works - this is for my written stories for Fanfiction(dot)net.
Then of course there's the books...on military aircraft...and using OPNAVs to give a representation of Carrier Naval Aviation. Using checklists to give an idea of authenticity to the naval aviation operations and reading and asking questions of those who actually fly.
My wife says I'm obsessive when it comes to accuracy - I try to get as close as I can...but since I haven't had the military experience, I'll never be able to get it 100%. Just close enough for horseshoes and hand-grenades. :D
And with the research that I've done, Homeland Security would put me on a No-Fly list... Nuclear weapons, IEDs...etc etc... :D Just writing a story about Afghanistan and some Al Qaeda boys going up against the JAG crew... :D Yeah...the good guys win albeit rather bloodily.
