Stardew Valley

Zordnil's solution is great for explaining how the heart system works in Stardew Valley. However, it does not really explain the fastest way to get all of the heart related achievements. The easiest and best method, in my opinion, to get this achievement is to get the recipe for Sashimi.

First, you must have an upgraded house with a kitchen. This will cost you 10,000 gold and 450 wood. The best way to get this is to fish nonstop and cut down trees in the forest south of your house. While doing this, you can start working on getting the actual recipe unlocked.

The Sashimi recipe can be obtained by reached a three heart level friendship with Linus, the man who lives in the tent to the north east, right next to the mines. You can give him many things, but the easiest would be yams in the fall because you can grow them. Note that you can only give him two a week, so either continue playing normally or sleep until the next week is available. If it is the third of winter, you can give it to him for a huge bonus as this is his birthday.

After you have a three heart friendship with him, he should send you the recipe the next day through the mail. All this recipe requires is one fish. So the whole reason behind making money with fishing is that your fishing level will be higher, which will let you catch fish easier. Also, you can purchase bait from Willy at the beach for 5 gold a piece if you have the Fiberglass rod (which will cost you 1800 gold at Willy's shop).

Once the recipe is obtained, all you have to do is fish and fish all day, then go into your kitchen and turn it into Sashimi. This meal is loved by Sebastian and liked by everyone but Willy, Emily, Evelyn, Kent, and Krobus.

So, essentially all you have to do is make sure that every week you give 2 Sashimi to the villagers you have decided to use to get this achievement. Remember to give them it on their birthday as well and you will have this achievement as well as all the other heart related achievements in no time.

The smaller details (such as heart score) of this guide are taken from http://stardewvalleywiki.com/Friendship

Your friendship level with most villagers is represented by a ten heart meter.
Villagers you can marry have their last two hearts locked until you reach 8 hearts and give them a certain gift (bouquet). Until the bouquet is given their heart meter is considered full at 8. As long as you are not married, you can give the bouquet to as many villagers as you like with no negative repurcussions.
Marrying someone will unlock two extra hearts plus an additional hidden heart for a total of 13.
Each heart is worth 250 points.
Certain actions/inactions increase/decrease your heart points with the villager in question.

Increases score:
+Talk to them (+10-20)
+Making certain decisions in heart events
+Completing a quest for someone (+150)
+Giving them gifts (love +80, like +45, neutral +20) This score is multiplied by 8 on the villagers birthday and by 5 on the secret santa event. The quality of the item gifted also affects the score
+Dancing with one of the bachelors or bachelorettes at the Flower Dance festival (+250, but need 4 hearts before they will accept to dance)
+Adding the right ingredient to the soup at the Luau festival (+120/60 with everyone)
Full list of good and bad ingredients can be found here: http://stardewvalleywiki.com/Luau
+Completing all bulletin board bundles at the community center will raise the player's friendship rating with every non marriage candidate villager by two hearts.

Decreases score:
-Not talking to a villager (-2/day)
-Hitting them with the slingshot
-Going through a trash can when seen (-25, but Linus doesnt mind)
-Giving them gifts (hate -40, dislike -20) This score is multiplied by 8 on the villagers birthday and by 5 on the secret santa event. The quality of the item gifted does NOT affect this score
-Adding the wrong ingredient to the soup at the Laua festival (-100/50 with everyone)
Full list of good and bad ingredients can be found here: http://stardewvalleywiki.com/Luau

You can only give a villager one gift/day and a maximum of two/week (you can always give a gift on someones birthday, even if you reached that weeks max).

Once you reach 10 stars (8 with romanceable villagers) it will not decrease if you ignore them. It can still decrease with bad gifts/actions.

Listing every characters loves/likes etc would take up several pages of text so i will instead link to where you can get that info: http://stardewvalleywiki.com/Villagers
Just click on the desired villager to see details of what they like and also their schedule for moving around.

Have fun out there and remember, no sex before marriage!
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Thanks to contributors:
ALollz
Kelle1994
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Writing guides/solutions is about helping the community, a lot of time can go into writing some. Thats why i wish that if you dont find the guide helpful you will leave a comment and tell the author what you dont think is correct or what might be missing so we have a chance to improve it for the next person who reads it. This way you help the community as well. Thanks!

In my initial Community Center playthrough this achievement glitched and wouldn't unlock, despite the other friend level achievements unlocking. If this happens, I can confirm that attempting this achievement again on a second playthrough (in my case doing a joja development run) unlocked the achievement for me.

I made up a simple strategy to speed through this achievement ASAP, but there may be some more optimal solutions.

Prerequisites

• Have access to the desert bus.
• Have enough sprinklers to water ~50 spaces. You can do this by getting to level 40 mines and farming enough iron and copper ore for 12 bars each, providing 12 standard sprinklers.
• Have a scarecrow.

Villagers
Here are the 10 villagers I aimed for, alongside the items I was collecting for them:

1. Abigail - Pumpkin
2. Demetrius - Ice Cream
3. Haley - Coconut
4. Harvey - Coffee
5. Linus - Cactus, Coconut
6. Pam - Beer, Cactus, Turnip
7. Sam - Cactus, Pizza
8. Sandy - Crocus, Daffodil, Sweet Pea
9. Shane - Beer
10. Willy - Pumpkin

You will need around 13-20 loved items per villager, depending on how long their friendship is decaying.

General Flow
All seasons:

• Keep crops constantly planted for an income stream. Just go for the most profitable crop from Pierre's/Sandy's for each month for simplicity. Don't bother using a watering can, just stick to the sprinklers so you can sleep through the week.
• You only need to be active on two days a week, as you can only gift villagers twice a week, resetting on Sunday. I would recommend you are active on Fridays and Saturdays, as these are the two days in which foraging items are the most abundant, before resetting on Sunday again. After harvesting items and gifting on Friday and Saturday, sleep through the week until you hit Friday again.
• When you gift a villager, make sure to also talk to them for an extra boost.
• Watch out for birthdays - birthdays do not count towards the weekly 2 gift total, so wake up specifically on those days for birthday gifting.
• Once you hit 5 hearts with a villager, stop bothering to gift them and focus on somebody else. It will be a few weeks before they go back down to 4 hearts, and a single gift and a talk will be enough to bump them back up.
• Coconut and Cactus are harvested from the desert. Collect them when visiting Sandy.
• Beer, Coffee and Pizza are easily bought from Gus in the saloon. I would recommend buying batches of 4 of each, so that you can gift Pam, Sam, Shane and Harvey in the morning via your stash instead of waiting for the saloon at 2pm.

Spring:

• Grow Turnips for Pam if you don't want to use up beer or cactus on her.
• Collect Daffodil for Sandy through foraging.
• Gift Haley on 14 Spring.
• Gift Pam on 18 Spring.
• Gift Shane on 20 Spring.
• Invite a character you have at least four hearts with to the flower dance on 24 Spring. This can be Abigail, Haley, Harvey, Sam, or Shane .

Summer:

• Collect Sweet Pea for Sandy through foraging.
• Buy Ice Cream from the Ice Cream Stand for Demetrius (1-5PM , Thursday - Tuesday).
• If you have an an appropriate item for the pot luck to gain positive favour with the governor (look for the luau on the stardew wiki to check), attend the Luau on 11 Summer.
• Gift Sam on 17 Summer.
• Gift Demetrius on 19 Summer.
• Gift Willy on 24 Summer.

Fall:

• Grow Pumpkin for Willy and Abigail.
• Gift Abigail on 13 Fall.
• Gift Sandy on 15 Fall.

Winter:

• Collect Crocus for Sandy through foraging.
• Gift Linus on 3 Winter.
• Gift Harvey on 14 Winter.
• If your secret santa is one of the 10 villagers, attend the Feast of the Winter Star on 25 Winter.