What your riyals are worth back home — today's rate, and your salary converted for the month and the year.
For most expatriate workers the riyal is only a staging post — what matters is what arrives at the other end. Two things decide that: the exchange rate, and what the transfer costs.
The Saudi riyal has been fixed at roughly 3.75 to the US dollar for decades. That means SAR rates against the rupee, taka or peso move almost entirely with the dollar, not with anything happening inside Saudi Arabia. When people say "the riyal is strong this month", what they usually mean is that their home currency has weakened against the dollar.
This page shows the mid-market reference rate — the midpoint banks trade at between themselves. An exchange house or bank adds its own margin on top, and often a fixed fee as well. The difference is usually small per riyal but adds up over a year of monthly transfers, so it is worth comparing two or three providers rather than always using the same one.
Because of the dollar peg, day-to-day movement in SAR rates is modest. Waiting a week for a better rate rarely gains as much as choosing a cheaper transfer provider once. The exception is a sharp move in your home currency, which is worth watching if you are sending a large one-off amount.