From the main startup screen, click Advanced, and then Preferences. Make sure "Sid's Tips" is checked (and anything else you'd like), then go back and start a game. This will give you popup hints and suggestions, as I recall.
Also, the "mouse over" feature works on pretty much everything in the game, no matter what screen you're in. This alone gives a wealth of information, along with little hints on how to use things.
Lastly, the manual can come in handy (mostly for keyboard shortcuts lol).