Flying from Belize City with Tropic or Maya Island Air is easiest. You can also ride a school bus into Placencia from Belize City; 4-6 hours. The road from Southern Highway to the village is rough and dusty - alternately take the bus past Placencia road to Independence and Mango Creek in Stann Creek and then the Hokey Pokey water taxi across to Placencia.
Just wear comfortable shoes. There are taxis, but you shouldn't need them except perhaps to/from the airstrip, which is only 10 minutes from town. "The Sidewalk" is a concrete pedestrian-only path that runs most of the length of the village, ending at the seashore. It is interesting to walk up and down and there are many businesses of all types along the way.
Buy from the locals. Maya women and girls typically line the sidewalk from the early morning hours.
The best seafood is at Lost In Paradise Beach Shop & Pirates Grill, located on the sidewalk in Placencia. Great baja fish tacos, ceviche, shrimp cocktails, nachos, burritos, tapas and philly cheese steak subs, vegetarian meals. Great affordable meals, small location, great food on the go. Breakfast, Coffee and Wifi available.
Actually, you can find quite a bit of good food and a few places for great food. A few suggestions would be Barefoot Beach Bar for burgers, smoked fish, smoked chicken and cold beer. French Connection offers limited seating and astonishingly good food. Tratoria offers good italian, theres another italian place above Wallens Market, that's also quite nice. If you want to spend a lot of money you could visit one of the resorts, though it's not the best way to spend your money. De Tatch is the best place for local food. Seafood, chicken and daily specials reasonable.
Belikin Beer (they also make a decent stout), or One Barrel rum, both products of Belize.
The local coconut rum is surprisingly good, and happy hour at the Barefoot Beach Bar (6-7pm) is the best place to be. They also have an excellent band on a Sunday evening, Inner Vibrations.
The very good artesian water from the tap.
Accommodation ranges from huts with shared "bathroom" to cabanas on the beach to guest houses to resorts. The resorts are north of the airstrip in Seine Bight and Maya Beach, and not really part of the village.
You can drink the water; it's plumbed in from an artesian well on the mainland.
Bring plenty of mosquito repellent.
Avoid any "locals" selling drugs. Most are not from the village.