When carving always use a bladed, sharp carving knife.
Use a stable carving surface, like a cutting board with a well or lip (to capture juices).
Carve Roasts perpendicular or across the meat grain.
Consider anchoring the roast with a carving fork.
Make sure you have plenty of space to work.
Roasts are firmer and easier to carve when allowed to stand 15-20 mins as the juices, which were pulled into the centre with the meat fibres contractions under heat are returned to a more even distribution as the meat fibres cool and relax.
Uniform, attractive slices are the best. For this, hold your carving knife at the same angle for each cut.
In general, carved slices should be thin 1/4 inch to 1/2 inch each.