Fire Emblem Fates - Tricks, Tips and Not Really Hacks

Tricks

Recruit or buy skills from more than one character from a Castle in a day

Say you found a castle where you want to recruit more than one character's abilities. 

1. On the battle preparations screen, save to a slot before invasion.
2.  Proceed to seize the castle/clear battle, buy a skill/recruit a unit.
3. Save in a new slot.
4. Restart game from Battle Prep screen.

Repeat as needed. The character / abilities will be in your logbook.

Visit a castle more than once a day

If you visit something between 25-30 castles after visiting a target castle (you can just enter one and leave immediately), you can visit the first target castle again. This is presumably because your game maintains a list of recently visited castles and the first castle was kicked off. 

This does not work if you try to access the same calling card twice in a day though. Enter via Castle Address search. Will update this after I've done more experimenting.

*Thanks to Useless Gross for telling me these two tricks.

Tips

What generally makes a castle a good visit?

• set of harder-to-come-by skills for characters you have access to
• easy to navigate layout
• resources
• not having to fight tooth and nail if you just want a quick skill-buy/recruit (referred to as "easy seize")

Visit castles based on rankings. The super high ranking ones are almost always "easy seize", translating into character good abilities and harvests with minimal effort. Get Calling Cards for castles you want to save to revisit later by talking to the owner.

Searching online through threads can also yield players who post their easy-seize, rare-skill castles addresses. Some are hit or miss though, as players change up their defenders and landscape since their posting.

Character planning: Public Spreadsheet in progress

Marriages - Children stats: Public Spreadsheet in progress

How reclassing and leveling works in Fates: Coming soon

Hacks

How do people hack and use cheats in Fates?

The short answer: 3DS Flashcarts. These are replacement cartridges loaded with software that you can modify to change how the 3DS reads games. These flashcarts, which allow you to play game images (ROMs), can be purchased from third party retailers, and may require a bit of research to get started up.

This is a whole other can of worms which I won't cover here. But to my knowledge, this is why some castles you see have all resources unlocked, characters with abilities they're not supposed to have (as in they're technically not supposed to be able to reclass to obtain the abilities), etc.

This all comes with a certain risk, and if you've updated your 3DS too often, some of the software/cartridges may not work with your system. If you brick the 3DS using the flashcarts, no warranty will cover it - it's all on you.

If you're interested in hacking, here's a comparison of several flashcarts compiled by Gbatemp.net .

For those who have already gotten their feet wet, a thread to get started with the hacking community is available on Serenesforest.net .

I don't hack. Will I be affected?

Because some hackers released characters with otherwise unobtainable abilities (most commonly - but not limited to - aptitude, which is only obtainable by Mozu and her child), there is a good chance you may accidentally buy or recruit characters with these hacked abilities.

Furthermore, castles with more than four resources are almost certainly hacked as well, and harvesting beyond four resources would mean you've benefited from hacking.

Links and Helpful Sources

Fates can be a real complex game if you want to theorycraft and number crunch for best stats, etc. Serenes Forest has a great compilation of detailed character/class statistics and other fine information. More verified sources to come.