Here's my method: I have a piece of clear rigid tubing a little longer than the height of my tank. I put one finger over the top end, plunge the tube into the tank above the snail, lift my finger... the water and snail rush up into the tube. Replace finger, lift out, deposit snail elsewhere. Sometimes they are stuck pretty tightly and you can nudge them loose. I get my snail on the first try about half the time. The reason this works for me is that I can do it quickly whenever I see a snail, without the hassle of reaching my hand into the tank. My 55 gal was getting overrun with these guys and now you have to look hard to find one. I know they are still there and would re-populate if I let them, so I pull out every one I can reach with the tube.
Hope this helps,
Kathy