Depending on your experience as a boardgamer (and being aquinted with game-mechanics), but Nations is only a heavy game because there are a lot of factors to consider, each with their own set of rules. But just like most games, it all boils down to making Choices.
The rule booklet is quite extensive, so i deviced a player aid to make it clear what there is to consider and why you want/need something. A sort of Follow-up on "You read the rules, now what?" to help you make those choices.
I welcome any (constructive) comments/remarks/requests to make it a useful aid.