Like everyone else said, for trolling, crimps all the way. If you happen to run out of crimps, or feel better tying a knot, for mono or floro over 50 lb., I use a knot that I've called the heavy mono knot, original I know

. It's real easy to tie, holds great, and is much more compact than a uni, which I use for lighter lines, by the way. All you do is once you pass the line through your hook eye of swivel, put your finger on the main line going to the rod tip. Wrap the tag end around the main line and your finger twice, then run the tag back through both loops around you finger, going from the hook toward you rod tip. Wet it down good, and pull it tight. This is the knot I use on all of my grouper rigs, and have yet to have any trouble with it.