Betws-y-Coed -> Trefriw: North along the B5106, which can also be reached from Llanrwst.
Colwyn Bay -> Trefriw: Head west along the A55, then south along the A470, cross the River Conwy at Tal-y-cafn and head south along the B5106, or cross at Llanrwst and go north up the B5106.
Trefriw -> Llyn Crafnant: Head up the steep hill north of the Woollen Mills bridge, follow the brown fishery signs, follow for a while through the woodland and eventually you will see the lake, the cafe sits on it's southern shore.