Cut the deck boards 1/8 inch shorter than necessary when cutting boards for around obstructions like water pipes to allow space for drainage.
Secure the first decking board by driving two hot-dipped galvanized nails side-by-side down into the deck joists at several locations along the board.
Measure, cut and place the second board next to the first. If you're using 5/4-by-6-inch pressure-treated boards, abut one board right next to the first board. The 6-inch-wide board will shrink enough to create the right spacing for drainage. If you are using 2-by-6-inch-wide boards, place several 16d nails between the two boards, allowing the head of the nail to rest on both boards and hold the nail in place. After nailing down the second board, slide the spacing nails out from between the two boards and use them between the next two boards.