If it's a squeak that changes with speed, check and repack your front wheel bearings. Do both sides since they should, at least theoretically, wear at the same rate. Also consider that it may be your pads riding on the rotor. Most people, when changing the disk brake pads, don't use never seize on the slider surfaces and that can cause the calipers to hang thus making the pad squeak against the rotor.
Also consider that the squeak, if it's proportionate to speed, could be your universal joints or carrier bearing. Sound does some funny things under vehicles.
If the squeak comes with bumps, check/replace your shocks. If the shock is wet in the least, it's probably bad. If the shock appears to be ok, consider that your control arm bushings could be dried out or going bad. Spray them heavily with a silicone based lubricant and then go for a drive that will move the controls arms to the full extent of their travel in both directions. Return home and spray them again and see if there is still a squeak.
Do not use WD-40 to kill a squeak. WD-40 is a dessicant and will dry out the rubber over time. Hope this helps!
Jeff