Best website I found for smokes+flashes is
this one. They have all main maps, show an overview of the maps and all the different flashes & smokes you can do. Each of them have a short video attached which shows exactly how to do them.
Spend some time on there and learn all of them.
Unrelated question:
Back in my 1.6 days I remember my team & I often participated in one-day tournaments. Usually they were hosted by random IRC channels, with some stupid prize for the winner (usually a server for one week or sg). These were quite cool because it helped us practice, and there was a "goal" to move up the bracket and win the tournament.
I can't seem to find anything similar for CSGO. Does anyone know if it exists?