To grip a skateboard, remove the old grip tape and clean the deck, then unroll the new grip tape and position it over the deck with the sticky side facing down. Use a screwdriver to press the edges of the tape down onto the deck, making sure it adheres well and is free of bubbles or wrinkles. Using a razor blade or skate tool, trim the excess grip tape around the edges of the deck. Finally, use a file or sandpaper to smooth the edges and ensure a clean, even grip.