I have completed all of Ryder's missions, and completed up to the "Drive-By" mission from Sweet. Now I can't find any more mission to enter. How can I find new missions?
According to the missions list found on: SPOILERS AHEAD WARNING! http://www.gta-sanandreas.com/guides/missions/lossantos.php your next mission set would be:
- Sweets Girl
But the link i provided should help you. Otherwice, missions are found on the map marked with a letter.
You mention on Atlas EU's answer that you haven't completed missions for Big Smoke yet. You usually need to have completed some, if not all missions for all currently active people before getting new missions.
Of the people/groups in Los Santos, here's the ones that will offer you missions (that I can remember off the top of my head):
- Sweet (Your brother)
- Ryder (Gang member/childhood friend)
- Big Smoke (Gang member/childhood friend)
- C.R.A.S.H ('Any means necessary' Cops)
- OG Loc (Gangsta friend)
- Caesar (Sister's boyfriend, Racing enthusiast)