Use a shingle scraper pitchfork or flat shovel to get under the shingles prying them up.
How to remove roof shingles yourself.
Remove shingles in a 2 to 3 ft wide section as you work down the roof.
Chances are the nails that will be securely seated in the wood so a bit of force will be needed with a twisting motion of the roofing shovel or spade.
Secure loose boards and cover large holes.
Remove the shingles in layers as you work your way up the roof.
The shingles will roll up like a ball in front of the fork.
Push the shingles down to the roof jacks.
Continue tearing off the shingles and underlayment until you reach the roof jacks then start over at the top of the roof.