Best way to trigger off camera flashes???

I have the canon ST-E2 transmittor & this works fine but the other day the flashes seemed to be going off when another person using a canon camera was taking pictures also.Is this common thing to happen (seems to happen when his pop up flash was being used).

Maybe I have a defective transmitter but the flashes were going off when he was taking pics,maybe a coincidence.

If so what would be the best device to trigger several flashes off camera without any incidents?

I don't have or have used an ST-E2 which uses IR to trigger flashes. Do they have different channels you can change to? I don't think a Canon popup flash is capable of triggering other Canon flashes. Must have been something else.

Best way to trigger is radio signal remotes like Pocket Wizards... but this option forces you to use the flash(es) in manual mode... always a trade-off.

if u want the best, get some Pocket wizards plus II's

A pop-up from another flash should not be able to trigger an off-camera EX (or compatible) flash set to ETTL wireless slave mode so, were you using an optical slave triggering unit to fire your remote flashes? If so, then that would do it. If someone else was also using an ST-E2 or a flash set to master mode and was interfering with your slaves, you can change the channel you're using to one of the other three unused channels.