Throughout the day, your shop will be visited by heroes, who will buy or sell your crafted items. Heroes will remain in your shop until you sell an item to them or refuse a sale. Your energy is capped by the level of your Counter.
Racks: Racks increase the energy gained per sale for a certain kind of items.
Dismissing a hero without selling to them does not affect energy at all. However, repeatedly dismissing the same hero will make him/her come less often.
Buying: Heroes will sometimes sell equipment to you. When they do, they sell it for 75% of the basic value you can sell it to them. You receive energy when buying from them. If you have a rack for the kind of item you're buying, you'll receive more energy.
Complimenting: You may also attempt to compliment heroes. Failed compliments cost 1 energy. Successful compliments award more energy if the item is more pricey and if you have less energy remaining. Some heroes are more likely to accept or refuse compliments. Oneira usually accepts them, whereas Garreth often rejects them. Except for gaining energy, complimenting has no influence on the game. An achievement worth gold and gems requires you to compliment heroes thousands of times.
Suggesting a different item to a hero costs energy. If there are 2 or more acceptable suggestions, you can hold down the suggestion button to select the item you would like to sell. Heroes will only accept suggestions that 1) they can equip and 2) are within 7 levels of their own. The XP gained in a transaction is roughly 20% of the item's price, so suggesting more expensive items is a good way to earn more XP per transaction.
Discounting and surcharging: Discounting reduces the price of an item you are trying to sell by 25% and gives you energy. You can discount the same item as many times as you want. Surcharging increases the price of an item you try to sell by 25%, and costs you energy. You can surcharge only once per sale. Heroes will not visit you more for discounts or less for surcharges. If you plan to compliment, remember that the energy gained depends on the item price. So you should compliment before you discount and after you surcharge. Surcharging/discounting may alter the price of an item, but not the XP awarded for the transaction.
Bargaining: When heroes sell you equipment, bargaining decreases the price they're asking for by 10%. You can bargain up to 5 times. Each bargaining costs the same amount of energy.
Surcharging without racks: This trick relies on the fact that energy can't go below zero. Start with zero energy. Then gain energy by complimenting heroes and discounting items. You don't need to sell these items to discount them, so keep them. Exit the discounted hero's interface without selling. Then talk to another hero asking for an expensive item. Surcharge it using the energy you gained from the discount, and sell. Now, down to zero energy, you can dismiss the discounted heroes and stay at zero Energy.
Amassing energy fast: Discount an expensive item, Suggest a low Energy item, and perform a discount sale. For example, you can Discount a 20 Energy item, Suggest an item worth 3 Energy, and sell that 3 Energy item at a Discount, retaining net 18 Energy.