ni-no-kuni-wrath-of-the-white-witch
I just got the second character in my party (Esther). Now I can exchange familiar between characters. I just have been told that some characters will be a better match with some familiars. I have also been told to go to into "Friend & Familiars" menu to check which match will be best.
I don't know what to look for making the best match between familiars and characters.
To answer your questions, in order:
The first two images are from IGN and show the locations of caves and forest dwellings.
Some of these locations are found in the story. If you visit the IGN map (http://www.ign.com/maps/ni-no-kuni-wrath-of-the-white-witch/world), you can filter for the locations and then select the bubble to determine whether or not it is found in the story.
This image was posted on a Japanese website, but is incomplete.
The red triangles indicate secluded areas that you will encounter during the story. As long as you play through the story and side quests you will not need to search for these. There is also a region, south of Ding Dong Dell, that only opens once finishing the main story.
The purple triangles indicate the locations of secluded areas that are not linked to any quest and are only found accidentally or with a systematic search (or with a map like this).
The colored letters indicate locations of regenerating items (the sparkly star spots), such as flora and spring water, and can be disregarded for your purposes.
Best Answer
Each character has their own "Favorite Genuses" of familiars. If paired properly, the familiar will gain a small (I believe 10%) boost to their stats. This stat boost is only dependent on which character has the familiar. You don't have to level the familiar with that character, whenever they're paired up you'll get the bonus.
You can check the Genus and Favorite Genuses in the "Friends and Familiars" screen on the main menu.
Once you're on the "Friends and Familiars" screen, highlight a familiar and press square. In the upper right of each character's familiar lineup, you'll see three icons that represent the "Favorite Genuses" of each character.
The genus of a particular familiar is shown using the same icon system just below the type of familiar, in the upper right of the screen.
Not all familiars are created equal, and there are some real winners when it comes to the familiars within each genus. I've got my suggested lineup (and where to catch them) for the main party members in my Ni No Kuni quickstart guide.