Match your line size to fish your targeting
Anyone who has ever stood before a display full of different brands and types of casting and spinning line knows that choosing line can be confusing. A person going after panfish or trout on a mountain vacation wants much lighter line than the one who is hoping to catch giant catfish in a large reservoir.
The pound-test rating listed on the box of line refers to the straight pulling strength of the line. For example, six-pound test line will withstand a straight pull of six pounds before breaking. Most people are surprised at how much pressure even a six- pound pull is. To check it out, tie your line to a scale, like the one you use to weigh your fish. Then pull on the other end of the line to bring the reading on the scale to six pounds. It takes a surprising amount of effort.
Abrasion resistance is especially important if you will be fishing around rocks, brush, heavy weeds, or other thick cover. If your line will be dragging over these rough surfaces, it needs to be engineered to resist snagging and nicks. Most premium monofilament lines such as Stren offer good resistance to abrasion, and there are lines formulated with harder surfaces designed specifically for extra resistance to abrasion. To test your line for nicks and scuffs that could cause it to break while you're fighting a fish, wet your fingers and run the line between them. You will feel any roughness that indicates abrasion. When this happens, cut off the rough length of line and re-tie.
When you tie a knot in fishing line, that knot is weaker than a straight piece of line. Premium lines generally have very high knot strength, and they will hold at or near the pound-test rating, even at the knot. Cheap line may have much lower knot strength, and may break at a fraction of its rated pound-test.
Controlled stretch and the proper limpness are two more features to consider when choosing line. All monofilament lines stretch when they are pulled, but some stretch too easily. Easily stretched lines lose strength and sensitivity. Line rated at 6-pound test is naturally going to be limper than 30-pound test line. But the brand of line you choose also has a lot to do with it. Premium lines are able to achieve higher strength with a thinner diameter and proper limpness
Line color is often an important factor. The better your line blends with the water, the more natural your presentation will be. Choose a good, quality line and you won't have to worry as much about breaking off when you've got the fish of a lifetime tugging on your line.
Our ancestors had to chase down wild horses to obtain hair from their tails to weave fishing line. I wonder if they selected horsetails for color and flexibility. Who knows -fishermen have always been a picky lot.