In general, I have used an Improved Clinch Knot. It is an easy knot to tie; holds strong with no fatigue on the line; and tends to cushion itself when a fish is on. I have used this particular knot for some 45 years now, with no failures of the knot. The only issue I have ever seen is if I do not wrap the line five times before securing it. Then, on light line (2 to 4 lb test), it might slip. Beyond that, no issues.