"can anyone suggest some steps..."

Step one for anything is always:

Read the Manual!!

Step 2: Visit the manufacturer's website & look for application notes; your distributor may also be able to help.

In particular, you will need to read-up on module's AT Command Set.
The standard command set is defined in the GSM Recs - along with all the other details of SMS and, in fact, the whole of the GSM system.
They can be downloaded for free from http://www.3gpp.org/
The specs you require are in the 07 series; particularly:
07.05: Use of Data Terminal Equipment - Data Circuit Terminating Equipment (DTE-DCE) Interface for Short Message Services (SMS) and Cell Broadcast Services (CBS);
07.07: AT Command set for GSM Mobile Equipment (ME);
07.08: GSM Application Programming Interface.

Tip: All modem (GSM or otherwise) AT command interfaces have a "Terse" and a "Verbose" response mode:
The "Verbose" mode gives responses like "OK", "RING", "CONNECT" etc;
The "Terse" mode gives only numeric code responses.
Obviously, "Verbose" is best for a person sitting at a terminal typing commands to the modem, but you will make a lot of unnecessary work for yourself if you try to get your 8051 to decode them!
For machine-driven operation, "Terse" is the way to go - in fact, this is specifically what it's intended for.