There are no written standards for SMS application design, so here are some guidelines. Please comment here or email me your thoughts.

1. Paginate clustered messages. See the Pagination section, below.
2. Answer ‘?’, ‘help’, and ‘info’ messages with helpful information. Including a link to a WAP or HTML web site with more detailed information.
3. Never use blank lines, which might confuse readers when they appear just above the fold. Use dashed lines instead to separate content.
4. When returning an error message, identify the problem, offer steps to correct the problem, and a link to more information (WAP or HTML).
5. Support common misspellings of commands, especially missed characters.
6. Always allow ‘Stop’, ‘Quit’, ‘Cease’, and ‘End’ to be accepted as a command to discontinue sending additional messages, such as to end a subscription service. Upon receipt of a termination command, it is acceptable to send a confirmation message, that may include instructions to restart the same service. However, never require a final confirmation, since the ‘Stop’ message is clear enough.

Pagination
It is not unusual for text message creation clients to support more than 160 7-bit characters, splitting outbound messages into chunks of 160 or fewer characters. Some user interfaces indicate the number of messages that will be sent, but none effectively convey the cost to the sender. Most clients simply indicate the number of characters that have been entered, and the consumer learns how many messages are sent after committing the Send action.
In your own applications that send messages in clusters, it is important to put page header information at the start of each SMS, indicating the current message and the total number. Ending messages that continue with “…” is also a good idea. AIM for SMS begins clustered messages with “FromName: -X/Y- ” and ends messages that continue with “…”

Since SMS delivery is not synchronous, “-2/2-” could arrive before “-1/2-”, potentially confusing users. However, delivery timing is out of the application designer’s control.

Designers have opportunities for creativity with pagination, but keeping it simple conserves characters. AIM for SMS uses seven characters to display “ -1/2- ”. The extra spaces and hyphens (‘-’) took up four out of 160… 2.5% for visual clarity does not seem like a bad tradeoff to me.