My best friend and I discovered that if you join each others game and fertilize the crops with the player who joined, you only have to use one. We can't figure out how to do it again.
Buying Missing Crops
If you are missing some crops simply go to a friends farm and find their roadside shop and tap on it and see what they are selling. Or if your level 7+ open your newspaper and see whats being sold.
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 thirty 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.
Easy Gold
First go to the roadshop and buy a new slot. Then on the one you bought, sell five pieces of wood and if anyone buys it, you will have 500,000 gold. Keep in mind; this glitch only works once.
Fast XP
Want to get fast XP? If you are level fifteen or up and you have apple trees, make sure you pick the apples as you will get seven 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.
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 ten wheat for $x).
Getting lots of extra items, tape, and more
Go to a friends farm and click on the toolbox. Sometimes it locked just click out of it but the reload the friends farm and find and click on it again. You can do this over and over again. When you reach your max u will continue to get the same item you last received.
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 buld (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.
Quick, Easy Money
Search through other people's newspapers for construction equipment like saws and dynamite and buy them in bulk (for example, five items for 400 coins). Then sell them individually for between 180 and 220 coins apiece. On the very last item you list place an advertisement on it so people can see ALL your items when they come to the store.
Roadside Shop
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 advertiment in the newspaper every 30 mins.
Wood Panels
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 your are havesting crops as they will just appear and go into your barn.
