How to get freight going from one city to another

The global market tab was originally designed to be a part of the Sim City World window next to the "Leaderboards" and "Challenges" tabs but it was removed before release of the game.

A pre-release version of the window can be found here.

Currently it appears that prices of goods do not fluctuate on the global market although on release day the prices were fluctuating seemingly randomly so it is likely a feature Maxis is tweaking to reduce server load.

If your city is out of power for whatever reason it seems to take a while after you get a power plant online for power to reach the entire city. First a power plant has to get workers, then after that it seems to take a while before it actually starts supplying power.

Buying power from other cities may be buggy. I played a city for several hours buying power from neighboring cities; then saved and reloaded that city the next day only to find the city without power despite power still being available in the region (it is possible that not enough power was available) so I broke down and built a power plant and observed the city slowly get powered up.