After the demise of Sunnydale, Giles and the others realized that the first and most important task was rebuilding. It was considered a prime opportunity – the chance to rebuild the archaic and antiquated Watcher's Council from the ground up. Giles, as one of the few surviving members of the old council, traveled home to England and used his connections there to find and gain access to the resources of the old council. Meanwhile, The Scooby Gang, Faith, and the rest of the former Potentials who survived the Battle of Sunnydale, along with Robin Wood, settled in Cleveland to start the rebuilding.
The first task was to find and locate newly called Slayers. Willow devised a spell that could pinpoint a majority of the girls, but eventually it was realized that it wouldn't be enough. Without Willow's magic to rely on, they would need other means. In the end, it came down to "on foot" tracking. With Giles gaining access to partial resources, Willow and Kennedy headed to South America, Xander to Africa, Faith to Australia and Asia and Buffy to Europe while Robin remained in Cleveland with Vi and Rona, monitoring the hellmouth there. Dawn, much to her frustration, was sent off to college in southern Ohio.
Within six months, funds were in the control of Giles, old watchers returned with the agreement to play by the new rules, and new Watchers were called. Leaving his distant cousin, Victoria Giles as the head of operations in Europe, Giles returned to Cleveland to assist in the efforts there. He'd learned from Robin that Cleveland clearly had taken the place of Sunnydale.
Soon after, Robin was dispatched, along with Vi and Rona, to Miami for a "southern hub," and Buffy took charge of operations in Scotland. Xander, exhausted from his travels in Africa, joined her there. Soon after, so did Dawn, who abruptly dropped out of college and ran to be with Buffy. The reason for Dawn's departure were soon discovered when she first changed into a giant, then a lady centaur, and went through several other mystical transformations.
Faith headed to Miami, but didn't remain long after a 'parting of ways' with Robin. She headed to Cleveland to regroup, and was surprised to be welcomed warmly by Giles and Andrew. Though her intention had only been to stay a few weeks, she took to training the new girls Giles and Andrew found, and soon found herself happily settled in Cleveland. She periodically leaves to hunt down rogue Slayers and reform them.
Dawn's time with Buffy was not happy. Buffy insisted that her sister take responsibility for her actions and refused to contact Willow to come to Scotland and restore Dawn unless it was proven that Dawn's life was in danger. When Dawn began to glow a pale blue, Xander decided that enough was enough and – against Buffy's wishes – contacted Angel to have Dawn transported to Cleveland where Giles could help her. When the plane arrived, Dawn begged Xander to go with her; she was embarrassed to meet Giles alone. Xander agreed, with full intents of returning to Scotland.
However, upon arriving in Cleveland, even restoration of Dawn had to wait. Slayer Central was embroiled in preventing an apocalypse and Xander was thrown right into the fray. When the storm blew over, Giles asked Xander to stay and train to do that very thing that he'd been doing all along: become a Watcher.
Xander and Dawn's "defections" disappointed Buffy, but Willow joined her in Scotland, and they work closely with Victoria and the Devonshire coven. Buffy, while overseeing Slayers, has no desire to actively take part in the field any longer. She and Willow do, however, periodically ask Xander to join them.
Five years after The Battle of Sunnydale, there are approximately 500 active Slayers around the world. The New Watcher's Council also has seers, psychics and witches in their service and partnership.
Aside from that one plane ride to get Dawn to Cleveland, Angel and his people, still in control of the LA branch of Wolfram & Hart (we'll happily ignore most of Season 5 of Angel), are considered non-entities. Wolfram & Hart is too much of an unknown, no matter how much Angel claims to be in full control, and Giles will not risk the New Council owing any favors to the evil law firm.