Quick noob wiring question

I feel a bit simple for needing to ask this, but:

I want to wire up a few LEDs so they all light up at the same time. I don't need them to be individually controlled.

Do I just need one resistor?

Does it matter if the resistor is on the anode or cathode?

I remember from physics lessons that I should wire them in parallel rather than series - does this actually make a difference to, say, nine LEDs on a decent power supply (PC PSU)?

Do I just need one resistor?

No one for each LED if they are in parallel. Just one if they are in series.

Does it matter if the resistor is on the anode or cathode?

No.

does this actually make a difference to, say, nine LEDs on a decent power supply (PC PSU)?

Yes if you wire them in series you need a higher voltage to turn them on, which means a higher voltage from the supply and a transistor to control it. Watch out for parallel connections as a pin can only supply 30mA of current. So you might need more than one or again a transistor.

Thanks grumpy mike :)