Is there a rule of thumb for a good trade? Such as 1ML = 2 prospects (3 if ML is superstar), or Cash = one player, or 2 pitchers = 1 position players etc. I want a good deal but don't want to make foolish offer or even an insulting one.

That's going to vary (greatly) by world, and even by owner within worlds.

Basically, it's whatever two individual owners agree on, and what at least most of the other 30 will allow.

In most worlds, it's going to be (potential) major league talent for (potential) major league talent, as long as it's not blatantly one-sided in one owner's favor.

Use trade chat to start a trade conversation. Plenty of times I've found what I think is fair is not fair at all in the other guy's eyes.

In chat, I usually try to get a conversation going about "how do you see" the players and prospects involved once initial proposals are out there. Do they see them as MVP caliber players, solid everyday players, platoon players, etc. If there are big discrepancies in perceived value, then there's not much you can do. If you can come to a reasonable agreement about what kind of impact players should have, it becomes easier to negotiate. A lot of owners naturally tend to over value their own players and prospects, so the point is often moot. But sometimes you can get an owner to do a reality check if you start a reasonable dialogue without denigrating his players. That tactic can come across as trying to diminish value.

Also, keep in mind, you're often going to be dealing with other owners who will feel that they have to "win" every trade they make. They'll be frustrating to deal with. Don't let yourself get bullied into a trade that doesn't feel right to you.

Thanks, great advice all.