I was wondering if there was some sort of cheat sheet for which objects go well with the using statement... SQLConnection, MemoryStream, etc.
If you are using Visual Studio you can press F12 on a type declaration it will take you to a meta-data screen or the class definition (if you have the source code). If you keybindings are different right-click and "go to definition". From there you can see what a class implements. I suggest doing this for all classes the first time you encounter them to get a "feel" for what the class can do.