Address review comments.

Author: jtattermusch

TROUBLESHOOTING.md

@@ -10,12 +10,12 @@ that gets printed to stderr.
 
 ## GRPC_VERBOSITY
 
-`GRPC_VERBOSITY` is used to set the minimum level of log messages printed by gRPC (supported values are `DEBUG`, `INFO` and `ERROR`).
+`GRPC_VERBOSITY` is used to set the minimum level of log messages printed by gRPC (supported values are `DEBUG`, `INFO` and `ERROR`). If this environment variable is unset, only `ERROR` logs will be printed.
 
 ## GRPC_TRACE
 
 `GRPC_TRACE` can be used to enable extra logging for some internal gRPC components. Enabling the right traces can be invaluable
-for diagnosing for what is going wrong when things aren't working as intended. Possible values for GRPC_TRACE are listed in [Environment Variables Overview](doc/environment_variables.md).
+for diagnosing for what is going wrong when things aren't working as intended. Possible values for `GRPC_TRACE` are listed in [Environment Variables Overview](doc/environment_variables.md).
 Multiple traces can be enable at once (use comma as separator).
 
 ```
@@ -24,10 +24,11 @@ GRPC_VERBOSITY=debug ./helloworld_application_using_grpc
 ```
 
 ```
-# Print info about invocations of low-level C core API.
-# Note that trace logs of log level DEBUG won't be displayed
-# as GRPC_VERBOSITY and GRPC_TRACE are 2 independent settings.
-GRPC_TRACE=api ./helloworld_application_using_grpc
+# Print information about invocations of low-level C core API.
+# Note that trace logs of log level DEBUG won't be displayed.
+# Also note that most tracers user log level INFO, so without setting
+# GPRC_VERBOSITY accordingly, no traces will be printed.
+GRPC_VERBOSITY=info GRPC_TRACE=api ./helloworld_application_using_grpc
 ```
 
 ```
@@ -37,6 +38,6 @@ GRPC_VERBOSITY=debug GRPC_TRACE=tcp,http,api ./helloworld_application_using_grpc
 
 Known limitations: `GPRC_TRACE=tcp` is currently not implemented for Windows (you won't see any tcp traces).
 
-Please note that the GRPC_TRACE environment variable has nothing to do with gRPC's "tracing" feature (= tracing RPCs in
+Please note that the `GRPC_TRACE` environment variable has nothing to do with gRPC's "tracing" feature (= tracing RPCs in
 microservice environment to gain insight about how requests are processed by deployment), it is merely used to enable printing
 of extra logs.