I've just started learning Led Zeppelin's 'Immigrant Song,' and I'm having a bit of trouble playing the bridge(?) part where it does those quick little 16th note runs. I'm probably an intermediate bass player. I have no trouble playing it at a slower speed, but when I try and keep up to the song I seem to stumble a bit. Should I be plucking each note individually, or hammering on to some of them?

Thanks =]

play each note with your right hand too. practice it with a metronome at a speed that you are comfortable with and gradually build up speed. it's really boring to do that but it's a great way for improving your technique.

I'm in the same boat as you. I guess I don't spend enough time practicing this song.

As with any tough section, isolate it, and play over and over with a metronome. make it into an exercise to warm up and down. Boring as sin but its the only way.
I'm on YYZ and theres about 3 sections in it that I use as warms ups.

After a couple of hours I pretty much have it now, feels good! Only thing is I can't seem to nail it standing up haha, guess I have to start slow again and work up from there :p

It's a pain in the arse though, my bass likes to dip down at the neck a LOT, which makes some things (such as this) a lot harder to do standing rather than sitting... oh wellll.

When I have a problem with getting the notes out, I start slow a measure at a time and try to sing the bass part. Then I make an exercise out of it (altering the rythmn or play in a different key).

or I play the same measure 3x slow and then try to double the speed for a measure or two.

yeah man that part is kinda hard. its a straoght mixolydian scale right?(guess i didnt get the spellings right) am practicing it everyday to nail it down at the temo of the tape.
untill then i just play 8th notes and i run through the scale in each bar once and not twice over and twice faster as jpj played it (not a good thing to do but it sounds ok and the band is also fine with it)