What items do I need to expose?

Only expose required fields and fields that are necessary for the actions exposed. Expose only those actions that are required for the consumer to perform their duty. All actions that are exposed need to be able to run in background without user interaction.

Though an entire table and even an entire system can be exposed via Web Services, doing so would affect performance and confuse users. Only the data that is needed by a client should be exposed. This prevents excess traffic and decreases the amount of storage that your client may need to use.