first strip the roof and replace any rotten wood, if you dont want to use hot pitch i would suggest using roofing felt with adhesive already on one side..first put the underfelt on, startaing at the bottom and working upwards, leave it short of the apex, and repeat the other side, finally put the last piece over the apex, making sure it laps over both sides at least 3inchs....the put the top layer on, allowing it to hang over the front and sides by atleast 2 inches, also try to keep the top of each strip is not in exactly the same position as the first layer...lay the top layer of felt as you did the first one...the advantage of using felt with adhesive on is there is no need to nail the felt, by putting nails in the felt you are damaging the integrity of the felt....if you want to do a good job I would suggest putting on 2 layers of underfelt before the green top layer...sorry if I have not explained it good enough.but hope this is of help anyway....its sometimes better to get a proffessional to do this with a guarantee,,,,but cost is the element....so good luck
phill
March 2008