Fishing hooks are one of the two most critical parts of your fishing kits, along with line. Ideally fishing hooks should be purchased ahead of time, but they can be improvised from safety pins, thorns, and many other common items. When purchasing hooks you should get several sizes to give you more options depending on the size of the fish you are trying to catch. Hooks sized 8 though 12 work very well for most freshwater applications. Simply put a number 10 hook can catch a 24 inch trout or 2 inch bluegill. Smaller hooks tend to do less damage and are easier to remove if one accidentally hooks themselves. Hooks can be purchased either snelled or not. A snelled hook is basically a hook that has been tied to 8-10 inches of fishing line with a loop at the end. Treble hooks should also be considered as they are more effective for certain applications.
When using a safety pin as a hook you must be very diligent because of the lack of a barb. Once a fish has been "hooked" you must keep constant pressure on the line.
A hook can be improvised from a rose or similar thorn by cutting a small piece of the stem with a hook shaped thorn at the very bottom. These are not the easiest hooks to use, but it can be done with some time and patience.
Aluminum Can Tab
A hook can be made from the tab from a soda can. Cut open one of the holes on a diagonal, pry open slightly, and optionally file until sharp. Line is attached to the remaining hole in the tab.
Tie a line in the middle of a small stick and sharpen both ends.