How to change your profession skills

Upon reaching level 5 and level 10 in each profession, you get to pick between two different skills. The level 5 skill will affect which skills you can pick up at level 10, and a lot of people wants so change their skills.
It is currently no in-game way to change them, but ConcernedApe says he is interested in making that available in the future.

Not being able to do it in-game does however not mean it's possible, and at the moment you can change your skills by editing your save file! This means editing the files where your save is located, so you should make a backup before you start editing, so that you can revert the changes in case you mess up.

Changing your profession skills

The first thing you need to do is find the folder with the save data. For Windows users its usually something along the lines of C:\users\Your_Windows_Username\appdata/roaming/StardewValley/saves/CharacterName_Number/

 Upon up the file called charactername_number with Notepad or another text editor and scroll down to the part that says <professions><int>7</int></professions>. Change the number 7 or whatever number you already have to match the profession skill you want using the table below.

Farming:
0 = Rancher: Animal Products worth 10% more.
1 = Tiller: Crops worth 10% more.
2 = Coopmaster: Befriend Coop animals quicker.
3 = Shepherd: Befriend barn animals quicker.
4 = Artisan: Artisan Goods(wine, cheese, oil, etc.) worth 50% more.
5 = Agriculturist: All crops grow 10% faster

Fishing:
6 = Fisher: Fish worth 25% more.
7 = Trapper: Resources required to craft crab pots reduced.
8 = Angler: Fish worth 50% more.
9 = Pirate: Chance to find treasure doubled.
10 = Mariner: Crab pots never catch trash.
11 = Luremaster: Crab pots no longer need to be baited.

Foraging:
12 = Forester: Wood worth 50% more.
13 = Gatherer: Chance for double harvest of foraged items.
14 = Lumberjack: Normal trees occasionally drop hardwood.
15 = Tapper: Syrup is worth 25% more.
16 = Botanist: Foraged items are always gold quality.
17 = Tracker: Locations of foragable items are revealed.

Mining:
18 = Miner: +1 ore per vein.
19 = Geologist: Chance for Gems to appear in pairs.
20 = Blacksmith: Metal bars worth 25% more.
21 = Prospector: Coal find doubled.
22 = Excavator: Geode find doubled.
23 = Gemologist: Gems worth 20% more.

Combat:
24 = Fighter: All attacks deal 10% more damage. +15 HP
25 = Scout: Critical strike chance increased by 50%.
26 = Brute: Damage is increased by 15%.
27 = Defender: HP is increased by 25.
28 = Acrobat: Cooldown on special moves is cut in half.
29 = Desperado: Critical hits are deadly.

Now just save the text file and restart Stardew Valley, and you have your new profession skills ready!

Source:  /u/Froghat_Vendor at Reddit.

How to obtain all the Rarecrows

The rarecrows are a collectible type of scarecrows that functions exactly like all other scarecrows in the game. There are a total of 8 unique rarecrows which can all be obtained in different ways.

1) Purchase for 800 tokens at the Stardew Fair.

2) Purchase for 2,000g at the Spirit's Eve festival.

3) Purchase for 10,000 Qi coins at the casino.

4) Purchase from the Traveling Cart during winter (it might not always be available for sale).

5) Purchase for 2,500g at the Flower Festival

6)  Donate 54 items to the museum.

7) Donate 40 items to the museum.

8) Purchase at the casino.

How to unlock the sewers

In order to unlock the sewers in Stardew Valley you need the Rusty Key. You get this in the mail from Gunther once you have donated 60 unique items to the museum, so go ahead and drop of all your artifacts and minerals. Once you have the key, go to the sewer entrance and use it, and it will be unlocked forever.

What can you do in the sewers

There is not a whole lot of content in the sewers, but there are a few things to do. Firstly you can catch the legendary fish Mutant Carp in there. This is one of the five legendary fishes, and can only be caught once in each save file.
Secondly you get access to Krobus, which sells a few items. You can also give him gifts to increase your friendship with him.

Krobus in the sewers.

Full list of items Krobus has for sale

Void Essence - 100g
Solar Essence  - 80g
Slime - 10g
Bat Wing - 30g
Lucky Lunch - 70g
Omni Geode - 300g
Iridium Sprinkler - 10,000g
Stardrop - 20,000g
Bullhead - 200g
Mixed Seeds - 30g
Autumn's Bounty - 400g

Most of the items rotate, so he usually only sells three or four items at the same time. The Stardrop can only be bought once.

How to get hardwood

Hardwood is a scarce resource in Stardew Valley, and once you have foraged all the stumps for hardwood on your farm, getting more can be pretty tedious. There is only one area in the game where you are guaranteed to get a steady supply of hardwood, and that is in the Secret Woods.

Finding the secret woods

The secret woods is a hidden area directly west of Marine's farm, so in order to find it simply go to the farm and keep going left until you stumble upon a tree root. Log this and keep going left and you will enter the secret woods.
Because you need to clear a log to enter it, you need an Steel Axe or one of higher quality.

Logging hardwood in the secret woods

Upon entering the secret woods, there are three trees readily available for you to log. This will give you 8 hardwood. However, there are also two "secret" stumps you can find by going trough a secret passage. It's somewhat weird to explain exactly the spot, so use the images below to locate it.

This area has two more stumps to log, giving you 4 more hardwood, for a total of 12.
The stumps respawn every single day, so you can get 12 hardwood each this with this method.

Other sources of hardwood

 There are also a few other ways to get hardwood, such as finding them in crates and barrels in The Mine or the Skull Dungeon. This method of getting hardwood is very unreliable, but is a nice bonus when exploring in the mines or dungeons.

Make some easy gold at the beginning of the game

Getting a steady cash flow of gold can be somewhat difficult at the beginning of the game, especially while you are waiting for your first crops to finish producing. There are however a very easy way to obtain a nice gold flow very early on, as early as day two.

What you need to do is gather 300 wood by chopping down trees on your farm or in the woods. This will probably take around one day, but as soon as you have got the 300 wood, head down to the beach (use the M key for the map if you are unsure where the beach is located). At the eastern edge you will find a broken bridge. This can be repaired using the 300 wood you collected, and opens up a small area with tide pools. The area itself is not particularly interesting, but it has a very high chance of spawning Sea Urchins and Corals.

The bridge repaired.

You will find a good handful of these upon your first visit, and the Corals are worth between 80g and 120g, while the Sea Urchins are worth between 160g and 240g, depending on the rarity of them. Most likely you'll find a good chunk of high quality ones, which can be sold for a few thousand gold!

Both Corals and Sea Urchins will respawn pretty frequently, so make sure to visit the tide pool area often. Once the bridge is repaired, you can visit anytime, so stop by every few days for your free and easy gold.