Fate of the Unwanted

Well, I havve been reading about radiant, and I understand it somewhat well, and I can now make maps and I know how to do certain things. Now, I needed to ask some of those veteran mappers out there for the answers to my questions, that is if they will bother reading this! First, I was wondering, how to make light entities and stuff, with the null and not null crap. Second, I need help in learning about shaders and stuff, maybe in a simple terms? And lastly, I was wondering about pre-fabs, and what they actually are? Any answer to these would be blessings, if ya can spare them! Me and a friend are taking on a rather ambitious job, (at least for us). I am going to try and make a map of what my school looks like. (My school aint that big) Anyways, plz answer these as quickly as possible, and thanks!

to make a light entity, right click and choose light... to edit it press n and type key light value (number) then right click on info_null to make that... put the info null where you want the light to point. then shift click the light first, then the null and press ctrl k...shaders are basically special textures, some of which do things and others are moving textures or glowing ones. shaders are indicated by a white box around them in the texture selector