Cut pork shoulder into large chunks
Season with salt, pepper, cumin, oregano, garlic, and chili powder
Heat oil or lard in a large pot or Dutch oven
Brown the pork on all sides
Add orange juice, lime juice, onion, garlic, and bay leaves
Add enough water to come partway up the pork
Bring to a simmer
Cover and cook on low heat until the pork is very tender
Remove the pork and shred it with forks
Return the shredded pork to the pot
Cook uncovered until the edges are crisp
Serve with tortillas, onions, cilantro, and salsa