The guys from the Maine BJJ academy, just posted a very detailed video about the Pendulum (flower) sweep. As always, excellent material from them to improve your game.
Another awesome video by Marcos Schubert from Gracie Parana. This time he shows a sequence of submissions from the guard (in Portuguese, but you can understand from just watching it).
The triangle is the "official" BJJ submission, yet very few people (specially white and blue belts) seem to get it right. These videos from Dean Lister and the Gracie Insider should be enough to understand how to do it right.
The guard is a ground position where one combatant has his or her back on the ground, while holding the opponent using the legs. To change from the closed guard to a more dominant position, you generally sweep your opponent.
To sweep from the closed guard, you have the following options:
Standing Sweep from closed Guard (when your opponent tries to stand):