Its personal choice , depends on where and how you hunt. Avoid the urge to change coils often during a hunt , its usually a waste of time and you wont remember where you hunted with what coil. Its good to have other coil options , especially the specialized ones like the sniper coil so you can set up the detector according to the specific site , but generally you want to try to hunt an entire site with one specific coil before changing and going back over all the same ground with another. There are so many variables , that you will learn , involved in coil choice and every site is different. Some sites you may want to change the coil for one better suited to them , some you may not need to change the coil at all , some you may have to hunt many times before switching the coil. Some people use more than one coil , some people never use more than one. You just figure out what works best for you after getting the experience.