When using an artificial lure, it is always advised to use a length of leader between the main line and the lure. In luring particularly, minimum diameter of main line is usually preferred for efficient casting and holding more lines. This translates to ability to use smaller and lighter reels and thus lurers won't get tired out easily from casting. Therefore a leader is needed to take on any abrasion (from fish bites or rocks) that is likely to happen near the lure.
Monofilament lines are usually used as leader for are not easily seen in water. It also provides the ability to stretch to absorb shock, especially if you're using braided or fused line as your mainline. You can use mono lines with extra abrasion resistance and low visibility like fluorocarbon lines. Do not choose leader line based solely on line weight alone (tested lbs) for it is not a direct factor of abrasion resistance. When in doubt, choose lines with considerable thickness over line weight.
There are a few ways to attach the lure to the leader. One way is to use a tie a loop through the eye or split ring of the lure using a loop (ie. Rapala knot). It has advantage of having minimal impact on the lure's action and cannot be easily be seen by the fish. Another way is to use a snap (see picture below), the advantage of it is that you can easily change lures unlike the previous method. The snap used should be as small and light as possible to reduce impact to lure action, with strength matching overall tackle. This points to use of high quality snaps for best performance.
For connection between the leader and main line, it's a good idea to use a barrel swivel to relieve line twist. You may opt to use a line to line knot to connect them but you may need to use a snap swivel on the lure attaching end. Line twist happens more often on spoons and jigs when retrieved back at high speed. Colour of barrel swivel should be black or dull in colour(non reflective) so fish will not mistaken it for a lure which usually result in the main line being snipped off.
1. The procedure is simple and straightforward. Cut a piece of leader line about 2 ft and tie one end with a snap and the other with a barrel swivel. Use Trilene knot on both ends.
