The lines will be easier to grab if they are elevated a little above the deck, you can get your fingers under them easier. Threading several beads onto the line works, tying a few knots in each line (double fishermans knot), or any hardware that keeps the line 3/8" off the deck helps tremendously. Even a figure 8 knot is helpful here.
Be careful that you don't leave the lines so loose that they will interfere with a roll. If the lines float out away from the boat while inverted your paddle may get hung up in them. Good deck lines are nice and tight and follow the contour of the boat closely, they should be strong enough that you won't worry about pulling hard on them during a rescue or for carrying the boat around but stay out of the way and pose no entanglement hazard.
Some kayaks now come with deck lines that have reflective ribbon woven into them. This provides a bit of extra visibility at night. These perimeter lines cost about three times what plain polyester costs.
Foredeck bungees (which are also referred to as a chart park) are often installed in a zigzag pattern, or in parallel lines 4-6" apart and running perpendicular to the length of the kayak. Zigzag lines do not work well unless they are spaced closely together.
Where decklines near the cockpit are used as one end of a paddle park, there should be a corresponding paddle park nearer the bow or stern.