The Minecraft Coder Pack contains Minecraft code that can be copied into your mod and modified to suit your objectives. It is an invaluable learning tool as well.
The Minecraft Wiki, “Creating mods” is probably the best place to learn about creating mods. What I have learned is that all mods are based on reverse engineering and then enhancing pre-existing Minecraft classes interpreted by the Forge project. This is why I have such great respect for my Mentors who are identified in the
Blocks don’t have to be cubes. Creating a non-cubic block is tricky but Mr. Crayfish has created a program to help simplify making the block model simply called “Model Creator“.
The Minecraft ID List provides basic information about all of the vanilla blocks and items in Minecraft. A tip of the hat to Graham Edgecombe for providing this useful information.