When writing in first person, how do you establish the "timeframe"? For example (and I believe this is what that thread answered), if I write...

"I walked into the room and saw a woman in the shadows. She moved into the light and I recognized her as Janice."

The question is, if the author is writing, then at this time he would already know it was Janice. Would you simply write, "I walked into the room and Janice was standing in the shadows?"

It seems that you'd remove any suspense from the story by doing this too often. Does that mean that some stories are better suited for third person writing?

Can you write first person (effectively)in past tense, but almost as if it's happening in the present (like the first example)?

If uncertainty about her identity isn't material to the plot--and the suspense isn't authentic in the sense of not being a feeling MC would have had--then your second version would be the one to go with.

First person narrative - how and why - http://www.hatrack.com/forums/writers/forum/Forum1/HTML/000394.html

There is a lot of gray area on this one. Depending upon the motives of the story-teller, they need not tell you everything that they knew at the time, let alone what they know now. Telling you everything they know now would be a boring story. Telling you everything they knew at the moment of action is almost always the right thing to do, but you can also establish an unreliable narrator. In fact, I just finished reading a murder mystery written in first person in which the narrator himself was the murderer! The way it was done, it was brilliant and did not feel at all like a cheat, because the narrator was recording the information for others to read and so of course would not want to implicate himself in the crime.