Hi Virginia,
I think when I started writing, I always did omniscient POV, but at some point switched to first person - sometimes Clark, sometimes Lois. (I did one from Martha's and one from Jonathan's, but those were really hard for me.) Now, I can't recall the last story I did that wasn't first person.
I do find it harder to remember what the person I'm writing from knows and doesn't know in long stories. I wrote a story several years ago (well, most of my stories were written several years ago at this point) from Lois' POV. Clark was in a relationship with someone else. I really wanted to show the dynamic of that relationship, and so would write scenes where Clark was out on a date and then remember that I couldn't use them since Lois wasn't there.
Similarly, I wrote a story from Clark's POV and in it, Lois was a bit... fickle, I guess. The things she did always sort of surprised me, even though I wrote them, and I often felt like I had to imagine the whole scene again in my head from Lois' POV to make sure there was some explanation for her actions, even if Clark didn't know what it was, as I wasn't sure she wasn't just acting crazy (she wasn't).
But both of these happened early on in the stories. Once I was several chapters in, I became ingrained in seeing it only from the POV I wanted. I actually had to take a break from the Lois one for a little while as she was going through something tough and whenever I even thought of the story I immediately got into Lois' head and then feel terribly depressed.
So, I guess over time it gets easier. You start to feel a bit more like you're one with the protagonist.
As for things to watch out for - just re-read often - especially early on - for scenes that slipped out of the POV you wanted.
Also, remember when you can to describe facial expressions, hand motions, etc. The little things that people do that let you know how they feel. It's those details (as noticed by your protagonist) that help people connect to the other characters, too. Even if Lois doesn't know why Clark is suddenly unable to meet her eyes and so she brushes it off, those cues really help a first person story end up with several well drawn characters.
Hope that helps.
- Nancy
