30 day trial means you keep your character and any accomplishments it did. You'll keep all your previous ranks without having to do anything.
The NPC that does your evaluations will keep you updated on your status. You can rank up once every 5 days; in fact that's recommended, since you have to learn less AN to qualify for a rank up. (I think the current formula guess is at least 4,000 AN prior to the 5 days ending, of which at least 2,000 must be earned through Campaign Battle.) The longer you wait to do an evaluation, the more AN you have to earn. If you keep on top of it and make sure you earn your 4K AN before the 5 days are up, you can climb through all 20 medals within a mere 100 days.
The NPC will tell you any of the following messages:
1. You can't get another evaluation for X number of days
2. The Allied Council was not pleased with your performance (less than 2,000 total AN earned)
3. While the allied council found your performance acceptable, they did not think it merited further honors (2,000+ AN earned, but less than 2,000 in Campaign Battle)
4. Congrats, you've earned a new medal (4,000+ AN in 5 days - or more if it's been more than 5 days)
5. The power of your current medal is too weak (30+ days have passed since your last evaluation.)
____________________________FFXI: Catwho on Bismarck. Once again a top bard on the server: Dardaubla 90 on 1/6/2014
FFXIV: Katarh Mest on Lamia - Member of The Swarm and the League of Extraordinary Crafters
I can't understand anyone who skips the cutscenes of a Final Fantasy game. That's like going to Texas and not getting barbecue.