You've got a few options with the miter joints for the legs and aprons. You could use splines, biscuits, dowels, screws, or a lock miter router bit to add mechanical strength to the joint. I have used a lock miter bit with good success, but it requires a careful setup to get good results.
For the tabletop, you'll want to allow the top to move seasonally so you don't want to rigidly fasten it to the aprons. Look at the figure 8 brackets at a woodworking store for a great option for securely attaching the top while still allowing seasonal wood movement.
For the tabletop, you'll want to allow the top to move seasonally so you don't want to rigidly fasten it to the aprons. Look at the figure 8 brackets at a woodworking store for a great option for securely attaching the top while still allowing seasonal wood movement.