AutoCAD 2010/2011/2012 DWG Format

[#1]

My design center has the content of my entire computer on it. How do I adjust it so that only the general blocks are present on there, such as doors, plants, etc.?

[#2]

You are better off making tool palettes for specific/comonly used items.  

[#3]

In DC navigate to the folder where you keep your library drawings (drawings that contain your blocks, or a folder with your individual drawings for insertion), right click, pick Set as Home.  Now when you go to the DC, pick the home button, upper middle of the DC and you will be taken to that location.