diff --git a/HACKING b/HACKING
index d9a7d08..646e6d2 100644
--- a/HACKING
+++ b/HACKING
@@ -17,9 +17,25 @@ summary about it, although we don't follow all their recommendations:
 
      class UnreachableNetworkError(NetworkError):
 
-- Function parameters do not need to follow the break lines, pointed,
+- Function parameters do not need to follow the break lines pointed,
   but must follow the 80 columns rule.
 
+Also, other rules we follow:
+
+- All string formating must have the variables in parenthesis. In this
+  case, this is wrong::
+
+     text = '%d characters' % count
+
+  this is right::
+
+     text = '%d characters % (count)
+
+- Unless it's a work in progress, do not leave code commented (or,
+  worse yet, inside a ``if 0:`` block.) If it's a WIP, be sure to
+  comment what it is (e.g. "Working on issue #X" or "Trying to make
+  the field count properly".)
+
 
 Documentation
 =============