Source code to get Delphi to talk to AutoCAD

Does somebody have some good sourcecodes that I can use, to learn how to let Delphi 4 talk with Autocad R14.01 and what things I have to load and set before I all works, I have tried to load Acad.tlb as an unit into Delphi, I can't Delphi open an new drawing in AutoCAD, what's the next step ????

Example:
If i hit button 1 there must be an line drawn.
If i hit button 2 there must be an circle drawn.
And what about getting information from lines and other elements into Delphi.

I hope somebody can help me with this problem.