How to get money VERY quickly
To get money extremely quickly in Hay Day, first go hunting through your newspaper and other people's newspapers for construction equipment and saws, dynamite, and other goods selling in build (i.e. 5 for 400 or something). Buy them all. Then, turn around and sell them individually for between 180 and 220 coins apiece, and put an advertisement on the very last one you list, so that when people go to the store, they will see all of them.
Diamond Trade Swap
Look for a farm called 10=1 diamond run by kyleigh.. I'm not sure how it works but every 100 you spend you get 1 free diamond... I'm currently on 20 diamonds. Check out how you can get more diamonds in Hay Day.
Getting lots of extra items, tape, and more
Go to a friend's farm and click on the toolbox. Sometimes it's locked; just click out of it but then reload the friend's farm and find and click on it again. You can do this over and over again. When you reach your max, you will continue to get the same item you last received. For more bolts, screws, tapes, check that link out.
First go to the roadshop and buy a new slot. Then on the one you bought, sell 5 pieces of wood and if anyone buys it, you will have 500,000 gold. Keep in mind; this glitch only works once.
The Mystery Box is behind the house
... and you can’t get it!? Tap on the twinkling lights that float up…it will open.
Related: How To Collect Diamonds in Hay Day
Hay Day iPhone Cheats - GameRevolutionWATCH GALLERY
Want to get fast XP? If you are level 15 or up and you have apple trees, make sure you pick the apples as you will get 7 XP per apple. Try and find apple advertisements in the paper, then visit the people that have apple advertisements, then search their farm for shaking trees with exclamation marks on a sign. Click on the sign and you get an XP reward. Complete orders on the order board. Visit other people's farm and look at their dock; if it has a crate with an exclamation mark, click it and take a look at the supplies you need to get an XP reward.
Cats and Dogs
You can buy the cats and dogs with vouchers and you gain vouchers from completing boat and truck orders or harvesting crops and treasure box. You can not trade them. When you have enough vouchers you can buy your cat or dog, but before you do this you must buy a cat or dog house. Your cats and dogs will need feeding, milk for cats and bacon for dogs. Every time you feed your pet you will get 30 xp. They only feed every few hours. Apart from the xp they are mainly a decorative purpose for your farm; for some players, this will be a personal achievement getting each individual pet.
Finding Missing Crops
If you have run out of a certain type of crop, go into your friend's tab and select Greg. Enter his roadside shop and buy everything that is there. Sometimes there is even some tools there for a very low price. If Greg does not have what you want, visit other farms and go thought their newspapers and buy what you need in bulk (like 10 wheat for $x).
Provided you have an available slot, you can sell stuff at the roadside shop as often as you want. You can only get a free advertisement in the newspaper every 30 minutes.
These can either be found in the treasure chests or you can buy them with your diamonds. A good place to find them is when you are harvesting crops as they will just appear and go into your barn.
Buying Missing Crops
If you are missing some crops, simply go to a friend's farm and find his or her roadside shop and tap on it and see what they are selling. Or if your level 7+, open your newspaper and see what's being sold.
Buy a lot of wheat until silo is full, plant half of it, then turn your device up right and shake it while cutting down wheat. You will get free items.
Open your mine and use TNT. It will produce diamonds every couple of blasts. When you have enough diamonds, pay for Tom's service and have him find nothing but TNT and load up on it. Then blow the mine and use as much metal as you can; again, more diamonds will come every couple of blasts. Sell what metal you can't store. But you have to use Tom and get a bunch of TNT. For more ways to get diamonds in Hay Day, click there.