How Much of a Deposit Should I Give?
Usually the deposit demonstrates your seriousness of intent to purchase. It gives the seller evidence that you will go through with the sale. It's not the same as a down-payment. It gets credited towards the purchase price, on closing. How much? Nothing is cast in stone; it doesn't have to be a certain percentage, but generally the larger it is, the more serious the seller thinks you are.

Fixtures and Chattels: What are they?
“Fixtures” are generally considered to be permanent improvements to a property and they stay as part of the sale, on closing. If there's any doubt, have them listed as part of the offer. Give an exact description.

“Chattels” are considered generally as moveable pieces, or personal property. Some of these could be included in the the price, like a fridge or stove, etc. List them in the offer. Mention the make, model, serial number, if possible. Just because you think they are staying, doesn't mean that's what the seller is thinking... write it in the offer!

Irrevocable Date: What Does That Mean?

• Means how long you want your offer to be good for
• Could be a few hours, a few days or weeks, depending on many issues
• Your agent will advise you, but it's your decision