(S/E) From the north end of the lay-by, cross the A81 onto a single track road at the other side, passing some houses on your right.
Continue gently uphill for approx 800m. Along the way you'll pass a house on your left, cross a bridge over a burn and then pass a third house.
(1) Just beyond the third house you will reach a wide track which you cross straight over (East) onto an open grassy area.
(2) Follow a grassy path leading towards some trees at the foot of Dumgoyne Hill and after crossing over two stiles you are ready to start your ascent at a particularly boggy area!
Take care at this point: the most obvious track heads east towards the summit of Dumgoyne Hill. Whilst you can go that way, it is extremely steep and is actually unnecessary, so instead.....
(3) Look out for a track which bears left (North East) from just beyond the stiles at (2). Note that it is very easy to miss this fork (see image on Gillian's Walks for an illustration).
(4) Walk uphill for a distance of 400m then keep left (East) at a fork at 280m elevation to skirt around the side of Dumgoyne Hill.
(5) The land soon starts to flatten out. 500m along at a crossroads continue ahead (North East).
From here the track begins to climb again. Continue in a north-east direction, gaining height for the next 1.2km, and ignoring any trails off to either side of you.
(6) The track goes around Garloch Hill.
(7) Continuing north-east, another 600m along the trail you will pass through a fenceline.
(8) 1km along from here you will come to a fork - keep right (East).
(9) The path soon changes direction (South East) to reach the summit of Earl's Seat. To reach the trig point you need to climb over the fence.
From the summit, retrace your steps back to the lay-by (S/E)