as my teacher aka @Madhouse12 told you about the connections.....
now some points, if you add 3LEDs in a unit and add one resistor(200ohm) with them...agr un may say koi 1 b kharab ho gae to teeno band ho jain gi....but less effort is required to make these connections....
on the other hand... 1LED per unit and one resistor with each(470 ohms)....more effort of is needed for these connections....and now if any one LED got burnt only that LED will not work and it have no effect on the other LEDs...
i hope every thing is clear...
if having any other connection feel free to ask 