diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 211472e04..bb1897066 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -10,6 +10,7 @@
 * When breaking on binary operators, put the operator at the beginning of the new line.
 * Do not use aligned indentation. Indentation should always be block indentation.
 * Always use spaces for indentation.
+* Blank spaces should be avoided except around the import section at the top.
 
 ## Imports
 
@@ -53,17 +54,19 @@ FN!{stdcall DRAWSTATEPROC(
     lData: LPARAM,
     wData: WPARAM,
     cx: c_int,
-    cy: c_int
+    cy: c_int,
 ) -> BOOL}
 FN!{stdcall NAMEENUMPROCA(
     LPSTR,
-    LPARAM
+    LPARAM,
 ) -> BOOL}
 ```
 
 ## Constants
 
 * Convert macro constants to Rust constants.
+* Numeric values should be formatted identically to how they are in the source file (don't convert
+  hex values to decimal, preserve capitalization of hex values, etc.)
 * The type of the constant should depend on where the constant is used. MSDN may help for this.
 
 ```C
@@ -75,6 +78,9 @@ pub const CLSCTX_INPROC: CLSCTX = CLSCTX_INPROC_SERVER | CLSCTX_INPROC_HANDLER;
 
 ## GUIDs
 
+* Numeric values should be formatted identically to how they are in the source file (don't convert
+  hex values to decimal, preserve capitalization of hex values, etc.)
+
 ```Rust
 DEFINE_GUID!{GUID_DEVCLASS_SENSOR,
     0x5175d334, 0xc371, 0x4806, 0xb3, 0xba, 0x71, 0xfd, 0x53, 0xc9, 0x25, 0x8d}
@@ -137,20 +143,22 @@ interface IDWriteFontFileStream(IDWriteFontFileStreamVtbl): IUnknown(IUnknownVtb
         fragmentStart: *mut *const c_void,
         fileOffset: UINT64,
         fragmentSize: UINT64,
-        fragmentContext: *mut *mut c_void
+        fragmentContext: *mut *mut c_void,
     ) -> HRESULT,
     fn ReleaseFileFragment(
-        fragmentContext: *mut c_void
+        fragmentContext: *mut c_void,
     ) -> (),
     fn GetFileSize(
-        fileSize: *mut UINT64
+        fileSize: *mut UINT64,
     ) -> HRESULT,
     fn GetLastWriteTime(
-        lastWriteTime: *mut UINT64
+        lastWriteTime: *mut UINT64,
     ) -> HRESULT
 }}
 ```
 
+For COM interfaces without a UUID, a UUID of all-zeroes should be used.
+
 ## Organization of code
 
 * All definitions go into the source file that directly maps to the header the definition is from.