Hi you definitely need to understand ohms law and know your batteries limitations. You will want to do the formula from ohms law as to not exceed your batteries limits. You will absolutely need a ohm meter to check the ohms of your build. It all depends on what your wanting to do, what your goal is, and what equipment your using. If your using a mechanical mod, obviously their will be no safety features built in so it will be up to you to do the math and not exceed your specific batteries limits. If you have a regulated device like say a dna 30 it will regulate for you and will sub ohm down to .3. A regulated device won't run a short in a coil, a mechanical mod will. We need more information about what equipment you have and which rba are you building. If you want to start out simple a great beginner rda is the kayfun. It gives loads of vapor and has a great flavor. But what exactly are you looking to do? Is your mod mechanical or a regulated? What are you trying to achieve? Their are many many coil builds that will each yield different results depending on what your wanting. Start out simple. Hope this helps