I've been very happy with a couple different versions of the TLR1. Go for one with a LED, the light is much brighter and the batteries last longer. I'm not up on the Shield series, but some of the smaller handguns need a smaller light, largely because of the limited rail space. Read the product information carefully. Keep it simple, you want a light, not a laser, strobe light, rotating beacon, siren, etc.
Now then, the ancient "hold the light high and to the side & forward of the body" concept was for searching-in the open. If you've never tried it for shooting, it's far, far less than optimal (Been there, done that, the T shirt didn't fit). That's why the various other techniques where the light is right by the handgun were developed. And, why the later concept of the gun mounted light was developed.
Also, within the home/office/school and so forth, you have many reflective surfaces- mostly your light colored walls. It doesn't much matter where you hold the light, there's enough reflection to make you clearly visible to any potential adversary. It's your cotton picking house. Turn the bleeping lights on!
Mas is making fine legal points that also involves human performance issues. [BTW, if you live in Virginia, there's case law that says you can't assault someone with a firearm (point it at/near them) for mere trespass.] I happened to be watching an episode of On Patrol (live) last night and watched an officer who was using a hand held light to search for an suspect in a stabbing. His gun hand held his service pistol-with light attached down at his side. If necessary, he'd drop one and use the other. Outstanding use of resources.