You can follow the link to the PNR Blog to see the analysis of the various predictors.
/pnr/post/238051
1) Start-Intermediate Quota.
2) A constituent of the Remote Quota group. In this case, takes...
more... place when the intermediate station does not have a share of the quota from the originating station; i.e. GNWL. Thus making the relative quota small.
3) Confirmed tickets are issued from GNWL. For combined tickets (Having more than one people in a PNR), confirmed berths can also be given from Pooled Quota. (Depends on availability).
After the confirmed berths are exhausted, most of the times it directly moves to WL.
4) Moves slowly, supports RAC. Becomes handy when the train do not support PQWL.
5) To avoid landing up in RSWL, always check for stations beyond your preferred destination station supporting GNWL.
6) RSWL is usually followed by RLWL. Most of the times RLWL is not visible due to distance restriction and/or restricted booking/s.
7) Because of the above reason, confirmation chances of RSWL in Rajdhanis is pretty low or rather uncertain. Since the system would not allow booking for the latter part of the journey, it prefers to clear the GNWL booked from start-end.
8) A train can support more than one RSWL.