Resistors before every led?
You should use a resitor for every series string of LEDs.  Put as many LEDs in series as can be driven by the available supply voltage, minus a little.  Then size the resistor so that you get the right current thru the string.  Only string together LEDs that you want to run at the same current.

For example, let's say you have a 12 V power supply.  You have a bunch of LEDs that you want to run at 20 mA, and that drop about 2 V in the process.  6 in series would come out to 12 V, leaving nothing for the resistor.  Therefore, you'd put 5 in series.  Those should drop 10 V.  The resistor drops the remaining 2 V.  You find the resistor value by Ohms law.  (2 V)/(20 mA) = 100 &Omega;.  Since 20 mA is the maximum spec, and you therefore don't want to exceed it, the next larger common size of of 110 &Omega; would be appropriate.