get yourself one of those little probe things from an auto part store. it's got a needle on one side and a cable on the other.

hook the wire to a ground, and turn your blinker on. probe the wires under the dash (under the steering wheel) and probe for the wire that gives a pulsing signal when the left or right blinker is on and tap into them.

Here's a list of the diff wire colors... Don't see any for blinkers though so good luck..

Constant 12V+ White Passenger's Side Fuse Panel or Ignition Harness
Starter Black/White Near Heater/AC Fan Motor
Ignition Black/Yellow Ignition Switch Harness
Ignition 2 White/Black Ignition Switch Harness (ABS Light)
Accessory Yellow Ignition Switch Harness
Tach Blue Distributor
Brake Switch Green/White Brake Switch
Trunk Release White/Red (+) Driver's Side Grey Molex
Trunk Pin Orange (-) Driver's Kick GREY Molex Connector
Parking Lights Red/Black Fuse Panel
Head Lamp Blue Left of Column Blue Connector
Hood Pin Yellow (-) Passenger's Side Green Connector
Factory Disarm Blue Driver's Door
Door Trigger Black/White (-) Passenger's Side Fuse Panel
Door Lock Black/Blue or Black/Red Panel Passenger's Side near Door
Door Unlock Orange (-)
Horn Wire Light Green/Blue Passenger's Side Fuse Panel