Why is Affection Important?
Affection is extremely important while raising
a chocobo as it directly affects the progress
of stat advancement.

The basic tricks of the trade to advance your Chocobo's Stats are:
-  Checking your Chocobo daily:
   taking it on walks or reading stories
-  feeding it Carrots and Greens,
-  setting an appropriate Careplan

- all the while maintaining a high affection.
A positive bond between owner and steed is
necessary for its willingness to learn and
improve itself.
Therefore, a neutral (variations of likes) or unhappy Chocobo will advance stats very slowly,
causing unneeded and unnecessary frustration.


The 8 Levels of Affection
 
1.                  = Max =
it seems to regard you as its parent.
2.
It seems to want to be with you all the time.
3.
it seems to like you a lot.
4.                = Neutral =
it seems to like you pretty well.
5.                = Neutral =
it seems to like being around you.
6.
it seems to slightly enjoy your company.
7.
it seems to be able to endure your company.
8.                = Lowest =
it does not seem to care about you.

You will want to keep your Chocobo's Affection
at either - 1 - or - 2 -.
Stat improvements are noticeable with high affection.
I've noticed on many occasions that lack of affection was the reason behind others having problems advancing their stats.

Increasing your Chocobo's Affection:
 
1. Monitor your feeding based on your
Chocobo's level of Affection.
This should be a daily ritual.
First check your Chocobo's progress to
decide the portions of Carrots and Greens that you would like to feed it for that day.
Since your Chocobo's mood will vary on a day-to-day basis due to many factors (food, careplan, interaction, illnesses, random events), checking your Chocobo's status should be done initially before feeding it.

If your Chocobo has level 3+ with it's Affection (Likes you a lot or lower affection), you will want to primarily focus on giving it greens and consider holding back on carrots until the Affection is raised.
(hint:  you may want to check your Chocobo's status between feeding portions and activity,
as it will be affected instantly after)
 
Neutral Affection or lower needs emergency handling if you are concerned about increasing Stats.  Do not feed carrots in this case.
This would just most likely prolong this state.

2. Special Affection Foods
Greens are what help in augmenting a Chocobo's Affection.  However, there are a select few Chocobo foods which specialize in increasing Affection.

Namely a Celerity / Tornado (HQ Celerity) Salad will offer a healthy bonus to any Chocobo's diet.  It's a wonderful meal: having medicinal properties to cure almost any ailment, it's believed to help cure boredom and love sickness, and helps increase multiple stats simultaneously.
One Salad will instantly bring your Chocobo to Completely full, so if you start off your Chocobo with greens until it reaches almost full, feeding it the Salad at the last feeding will doubly increase it's affection.

The flipside:  Celerity Salads are not cheap.
Even crafting them (cooking) yourself isn't very cheap.  They can be bought with Chocobucks though,  or found in Hot-and-Cold.

3. Taking Walks
Your daily routine should consist of at least one walk a day to maintain adequate affection.
With some experimenting, you will see how often its necessary to walk your Chocobo.

Depending on its stage of development, you'll be able to chose between which walk you'd like to take it on.  As an adult, you have all 3 Walk Options:  Short, Medium and Long available.  Common sense should let you know that a Long Walk with increase affection a lot more than a Short Walk would.

Chocobos with low affection should be taken for walks and checked (and not taken for Races or read stories) until their energy bar is empty.  This will noticeably increase their Affection.  The sooner that's accomplished, the sooner you can get back to programs that increase their stats.

4. Restoration Drinks
Restoration Drinks can be crafted through Alchemy. The two Restoration drinks available are Chocolixir and Hi-Chocolixir.

How the Drink works:
After you take your Chocobo out for activities and deplete it's energy bar, this drink can restore partially or fully it's HP - which allows you to continue it's daily activities (allowing the opportunity to boost stats or affection more).

In regards to affection, this allows you to take your Chocobo on +/- 2 more walks, which may greatly increase affection.
As with Celerity Salads, the Chocolixir will bring your Chocobo to Completely full, so starting it off with a few greens and making sure your Chocobo does not reach Completely full, then finishing it off after it's HP bar is empty, is very advantageous.

The flipside:  Chocolixirs are not cheap.
Even crafting them (alchemy) yourself isn't very cheap.  They can be bought with Chocobucks though,  or found in Hot-and-Cold.
The Hi-Chocolixir is not available via Hot-and-Cold, only the normal Chocolixir.
                             - - -
Focusing on these food, walks, specialty foods and restoration drinks should alleviate the problem of low affection, without adversely affecting your Chocobo.  However, if this combination is not improving your Chocobo's mood and you need more drastic measures,
the below advice can be followed:

5. Worming your Chocobo
Cupid Worms offer a huge affection boost to Chocobo's that seem to be out of hope.
I've noticed the affection boost does vary so
you may need to feed a couple to notice any change.
However, with the good comes the bad.
While affection may be increased, your Chocobo's Strength and/or Discernment may be decreased.  These counter-effects also seem to vary and random a bit.  But there's the risk.
There are other Worms to choose from as well, but Cupid Worms offer the biggest boost.

6. Resting your Chocobo
You have the option to set your Chocobo on a Resting Plan.  I do not advise this plan, and
it really should only be a last resort used
when your Chocobo has run very low on both HP and affection.
The following days will carry your Chocobo through a dormant state.  It will be asleep until it decides to wake up, which could be 2 days or could be a week.
In some cases, your Chocobo will not wake
up for a very long time, and the remedy for this is to either give it a Chocotonic or Scold it (which guess what, lowers affection!)