Communication

I don't announce. Anyone who matters will figure it out or ask. Anybody else, it's none of their business.

You need to discuss with the other, ask whether the relationship is mutually exclusive before saying anything to others.

I try for as much transparency as possible.

If I’m chatting/texting, there are often several folks. I like talking to people and hearing their stories, too. If it’s long distance and little chance of meeting in real life, I don’t get serious; just enjoy the moment, and I make it clear there’s no obligation either way.
Dating in real life: one at a time, to see if it’s going to work.
Being as clear as possible using your words is best: no such thing as a mind-reader...so I speak up.
Exceptions as stated by limeysteve below?.

I always focus on one person when I'm with them. Except for those times when I'm with two or more at a time.

If asked, I will always answer honestly. If I'm getting serious, I talk with the woman to see if she feels the same. To me, its not important who brings up what or when. I am content being just friends. It depends on us.