Step 1 in how to shingle a shed roof: When you shingle a shed roof, remove any old shingles if you are re-shingling the roof of an old shed. Check if the old paper has damages, replace; patch the old paper with new. When you're shingling a new roof, be sure that the roof boards are securely fastened; have proper alignment. Be certain to nail that are not nailed in, down.
For extra weather-proofing and water-sealing, you could caulk between the roofing board seams.
Step 2 in how to shingle a shed roof: If you're working with a new roof, lay down roofing paper. Start at a corner of the roof and, from an edge to another edge, roll paper over the top. Inch inch of paper should remain as overhang on the end. Secure the paper with a heavy-duty staple-gun after cutting. Now do the other strip. Overlap with approximately 1 inch.
When enough strips have been laid to cover the entire roof completely, trim the paper on the ends for a 1/4 inch overlap.
Step 3 in how to shingle a shed roof: Begin laying the shingles by starting at the roof's lower edge. Be sure the first shingle row will over hang by 1/4 to 1/2 inch. Nail each shingle down as you lay it down on the upper edge. Use roofing nails. After you've finished the first row, begin laying the second. Be certain you overlap enough to give the roof a clean appearance. Once you've reached the top, start on the other side.
Step 4: On the top ridge of the roof, cap with over hanging shingles. Begin at one ridge end with one shingle you lay at an angle of 90 degrees to the row of shingles you've just laid. Nail shingle down. Nail another shingle. Make sure you overlap each by 1 to 2 inches. Continue and finish. You've got a nice shed roof! That did not brake the bank.