Restoring a database back to a point in time before full backup was made
Its very difficult to reverse engineer and interpret SQL T-log records. As mentioned there are 3rd party tools like APEX SQL Log , RedGate's LOG Rescue, Log Explorer

Also, there is an undocumented command fn_dblog that can be used as below, but you wont have the flexibility like 3rd party tools.

SELECT 
    [Previous LSN],
    [Current LSN],
    [Operation],
    [AllocUnitName],
    [Page ID],[SPID],
    [Begin Time], 
    [Transaction Name],
    [Lock Information] 

FROM ::fn_dblog(null, null)
GO


Paul Randal has described how to read from T-log with excellent examples -- Using fn_dblog, fn_dump_dblog, and restoring with STOPBEFOREMARK to an LSN .