To begin your search for the source of the leak, the first step was to find the leak inside your home. Once you have done that, you have to confirm that the leaking is an effect of a roof leak and not from another problem inside your home. Other things can also cause water leaks inside the home, potentially, poor plumbing conditions, condensation, roof scuppers, roof drains and even HVAC can cause it.
If you have established that the water leak in your home is caused by a roof leak, the next step is to find two fixed points in your living space so that you can measure the location of the leak. The end point should either be the roof surface or somewhere in the attic space. So the starting point should anywhere inside your home like the walls or the chimney.
After this, go to the underside of the roof deck and using the measurements taken from your living space, you may be able to locate the source of the leak. Try to observe the leak while it is active and then take note of the surface where you will see where the dripping or leak is coming from. Always remember that where the water is entering in to attic space can be somewhat different to where leaking is visible on the inside of your home. This is where your explorer side must come out and you should expand your search when you are in your attic.
The next step is to have another two fixed points. This time using the location as to where the water is dripping from your attic. Try to use points like vents, pipes or chimneys. If you cannot find any, you can also use exterior walls as the two points.
Then, carefully go to your roof and use the measurements you have taken and apply on roof surface. Bear in mind that you will need to adjust slightly your measurements because of the depth of some walls or the overhangs if you used exterior walls as your fixed point.
Using all the measurements taken, you may be able to determine the approximate location. Observing and inspecting in concentric circles can also help in this step.
If you happen to see any opening in the roof system, this can also be the major cause of your roof leak as this is vulnerable for penetration especially when it is raining.
When you do decide to call for professional help, do not forget to rule out all the other causes that may have caused the leaking in your home. These can include problems in condensation, plumbing, air conditioning or even pests.
If you wish to repair yourself the leak, make sure you know exactly the cause of the leaking and that you are equipped with all the necessary materials.