Developing systems of morality, outside of religious influence.

[The Grand Nudger]

Basically, one of the biggest things I’ve had trouble with since leaving Christianity is justifying my actions.  Before, when I needed to make an ethical decision, I would rely on the bible to tell me what to do.  Or, if that failed, I’d ask someone more educated in the bible than me, and they’d tell me the “best” interpretation.

I doubt that's even remotely true.  I'm willing to bet you stumbled through life making hordes of decisions with a moral component without ever even thinking of what magic book had to say on the subject.  Is there some problem with continuing to do what you've always done?  

Now, I’m aware that the bible isn’t any better of an ethical system than anything else humans have come up with - probably worse, in a number of ways, seeing as it allows all kinds of things I would, at least in a gut response, see as atrocities.  However, at least from the point of view of the people inside of their religion, they have a rock solid starting point.

"Pixies said so" is hardly a rock solid moral footing. It's not even morally relevant. Pixies can say whatever the hell they want.

I guess I’ve got my “shoulds” mixed up nowadays.  I come to an argument on whether or not someone should do something or not do something(abortion, animal rights, lgbtq rights, racism, etc), and it seems like the best I have to contribute is “I personally like/don’t like that idea”.  I’m aware that there are a number of different moral systems that aren’t necessarily religious(hedonism, utilitarianism, Kant’s theory, etc.), but I don’t feel at all qualified to just pick one arbitrarily and run with it.  Would it ultimately be an emotion-based decision, going with the one that just makes me feel better about myself?

How people might feel subject to a given x seems like it's a morally relevant consideration.  I don;t know why you'd stop with yourself, there, though.  

So anyways, for a TL;DR: how do each of you, personally, approach ethics?  Do you adopt a certain system, or do you use a more cobbled together way of approaching things?  How does one feel justified in applying their belief system to the world, if there’s no divine objectivity backing them up?

The same way that christians do, and the same way that former christian atheists do.  "Divine objectivity" is a bit of a misnomer anyway.  The mandate of heaven is subjective.