Add 'some tips' section to MongoEngine

docs/patterns/mongoengine.rst

@@ -110,7 +110,7 @@ Available operators are as follows:
 * ``exists`` -- value for field exists
 
 String queries
---------------
+::::::::::::::
 
 The following operators are available as shortcuts to querying with regular
 expressions:
@@ -125,6 +125,19 @@ expressions:
 * ``iendswith`` -- string field ends with value (case insensitive)
 * ``match``  -- performs an $elemMatch so you can match an entire document within an array
 
+Some Tips
+---------
+
+* Attributes can be set as ``unique``
+* ``MongoEngine`` creates the ``_id`` attribute automatically to acess ``ObjectIds``
+* You can add choices to string fields: ``StringField(choices=['Apple', 'Banana'])``
+* If you don't want your class name to be the same name as the collection, you can define
+  a ``meta`` class member and use the ``collection`` parameter::
+
+    class Movie(Document):
+
+        meta ={'collection': 'movie_documents'}
+
 Accessing PyMongo MongoClient
 -----------------------------