Ring Finger and Pinky On the fretting hand
 

Hi, I just recently started bass and have been wondering for quite some time. When playing an octave note, is it necessary to use my pinky? I find by moving my hand slightly and using my ring finger instead I can play most riffs smoother. What is the proper method? Or are both acceptable?

No rules man, just do whatever is comfortable for you and sounds good.

I play the octave with my Pinky finger due to the fact it takes very little effort/movement to quickly play it. But thats my person taste. If the ring finger suits you more then go for it.

Yeah, use whatever feels best. I usually use the pinky too unless I play the b2 right after or something more stretchy, a riff after the octave etc.

By "moving your hand slightly"...does the angle of your wrist change? That is, does the angle of your wrist resemble that of a guitarist? Ideally, you want all 4 fingers on the neck...looking down, you should be able to see the backside of your wrist (the side where the wrist bends in)...not the side of your wrist.
By playing the octave with your ring finger...what happens to the pinky? Does it disappear?
BTW, the ring finger is the weakest finger on your hand. That's science & anatomy.

You also want to work on finger independence.
In short, finger-per-fret (somewhere up where it's more comfortable, for now)...then try moving only the index finger...up-down, up-down...move down or up to the adjacent string & back...the other fingers are to remain still.
Then do the same with middle...then the ring...then the pinky.
Use your plucking hand to assist (holds down the fingers that should not be moving) because it will not be easy.

I have seen a few things that "work"...in the long run, though...things that "feel best" now are easier but technique is training your body to go outside what "feels" best. Unless you're a natural, it takes time...what is difficult now becomes easier later once muscle memory kicks in.

+100! In the long run, having four independant fingers will take you a long way. I was self taught, and never used my pinky at all. When I finally did get some lessons, the first thing my instructor did was make me work on that issue. I could never play a lot of what I do now without it...

River People
 

As a musical way to practice octaves, I use Jaco's song River People http://www.youtube.com/watch?v=jng_yZUc4F0

It moves around the neck a lot, and for efficiency, I use both middle-pinkie and index-ring to do the octaves. If you're like me and can't play it at full speed, use a metronome.

I use my index and pinky, middle and pinky, and index and ring to play octaves. For me, it depends on what came before the octave or what is coming after the octave and where the octave is being played on the neck. Whatever is going to be the smoothest or easiest.

Notice what the really good players in your genre use.
For punk, I could believe three fingers are enough.
For jazz or metal, not so much.

Punk is supposed to be "anti-technique" (rebelled against Prog Rock, Rocker with chops, etc &, possibly, Jazz Fusion). Somebody may be a Punk today...a Jazzer tomorrow. Since the OP is a beginner, why not get it "proper" now (easier) vs. later (more difficult).

I was just re-visiting Birds Of Fire last night (Mahavishnu Orchestra's 2nd album)...I don't remember the exact words but Jan Hammer was hoping this kind of music ('70s-era Jazz Fusion) would be looked upon as a time when being actually able to play an instrument well mattered...that is was a good thing.

It takes three times as long to fix a bad technique compared to learning it right the first time. You have to:
1) learn it wrong
2) unlearn the bad habit
3) learn it right.