Most growers germinate their seeds in a starter cube or seedling plug. Some growers use the wet paper towel trick or just simply plant their seeds into the medium that they will use for veg and/or flowering.
For beginners I recommend trying out the Propagator Kit, It comes with everything you need to give you a headstart with tools to aid you with transplanting your seedlings into your prefered grow medium.
Temperatures should be spring-like. Around 21° C (70° Fahrenheit) is the best range.
Optimal humidity for seedlings and plants in veg won’t be as critical as later stages, but low humidity may lead to the stomata closing even when the lights are on, which could damage the plant’s photosynthesis process. Keep it around 60%.