Update read and check command examples

docs/UserGuide.md

@@ -100,6 +100,11 @@ Format: `read <NRIC>`
 
 Examples:
 * `read S1234567A`
+  * Displays profile of patient uniquely identified by NRIC S1234567A. 
+
+Common mistakes:
+* `read S12345678` (NRIC must be in the correct format, and must exist in the system)
+
 
 ### Updating a patient's profile : `update`
 
@@ -214,7 +219,11 @@ Checks all visits in patient history.
 Format: `check <NRIC>`
 
 Example:
-* `check S1234567A`displays all visits in history of patient uniquely identified by NRIC S1234567A.
+* `check S1234567A`
+    * Displays all visits in history of patient uniquely identified by NRIC S1234567A.
+
+Common mistakes:
+* `check S12345678` (NRIC must be in the correct format, and must exist in the system)
 
 ### Cluster finding : `cluster`