Like Bob said, head first is ideal. If I'm netting a fish for myself I always lead it into the net and let it dive in headfirst if possible. When I'm fishing with a partner in a boat, I use a ridiculously large landing net so it doesn't matter how the fish goes in. And I do swipe at fish if I have a clean shot. The net I use is about 7 feet tall and 3 feet across the mouth so you have lots of room for error. People laugh at it, but not once they've seen it in action :) If you're fishing in a boat and you're serious about it, get the biggest net you can.

This is the one I use (with the black mesh)
http://www.americanmaple.com/relaunchpromar/grandehalibutsalmon.html