# If you know a solution is not far from the root of the tree:
"BFS"
# If the tree is very deep and solutions are rare: 
"BFS (DFS will take long)"
# If the tree is very wide:
"DFS (BFS will need too much memory)"
# If solutions are frequent but located deep in the tree:
"DFS"
# Determining whether a path exists between two nodes:
"DFS"
# Finding the shortest path:
"BFS"