Your offer is the first step to negotiating a sales contract with the seller. So take the time to consider the seller's reaction to everything you include in the offer because it is very important. Unfortunately, you can't just say, "This is what I'll pay." Since you are dealing with a large amount of money, both you and the seller will want to build in protections and contingencies to protect your investment and limit your risk.
In your offer include not only the price you are willing to pay, but other details of the purchase as well. Along with that include; how you intend to finance the home, your down payment, what inspections are to be performed, who pays what closing costs, whether personal property is included in the purchase, timetables, terms of cancellation, any repairs you want performed, which professional services will be used, when you get physical possession of the property, and the very important matter of how to settle disputes should they occur.
For both buyer and seller, the purchase of a home is a major event. Unlike any other purchase or investment, buying a home will truly affect your finances. Not only yours, but the seller's also, since (s)he will make plans based on your offer.
Your offer goes deeper than just money because in the short time it takes to write an offer, you are making decisions that affect how you live for the next several years, if not the rest of your life. The seller is going to review your offer carefully, because it also affects how (s)he lives the rest of their life.
If that sounds dramatic, it's simply because it's true.
Contingencies in a Purchase Offer
Most purchase transactions are completed without difficulties. However, keep in mind that problems can arise, and if they do you can cancel the contract without penalty. These are referred to as "contingencies" and you must be sure to include them when you offer to buy a home. A good example is when "move-up" buyers agree to purchase a home before selling their previous home. Even if the home is already sold, it is most likely a "pending sale" and has not closed. Therefore, you must make closing your own sale a condition of your offer. Failure to include this as a contingency can result in you making two mortgage payments instead of one.
Here are a few other common contingencies you should include in your offer: Successfully obtaining suitable financing for you next home, property appraises for at least what you agreed to pay for it, and the passing of any required inspections before closing/escrow occurs.
Contingencies protect you in the event you cannot perform or choose not to perform on a promise to buy a house. If you cancel a contract without having built-in conditions and contingencies, you put yourself at risk of forfeiting your earnest money deposit or a percentage of the sale price!

Or worse.

Earnest Money Deposit
When you have determined your offer price, the next step is to consider how large a deposit you want to make with your offer. The "earnest money deposit" should be large enough to show the seller you are serious, but not so large you are placing significant funds at risk. One possibility is to make sure your deposit is less than two percent of your offered price. If your deposit is larger than that, the lender will pay close attention to how you came up with the funds. This could put you in a situation where you may have to provide a copy of a canceled check along with a bank statement showing you had the money to begin with. Typically, this is not a problem, but if your closing/escrow period is short or if you are still putting together your down payment, it could pose an inconvenience. Another reason to limit your deposit is "just in case." Significant problems should never be completely ruled out. "Just in case" there is a nasty or prolonged dispute between you and the seller, the less money you have tied up in a deposit, the less money you have placed at risk.
As with practically everything in real estate, there are also exceptions to this rule. During a hot market there could be multiple offers on the property you are interested in buying. A large deposit may impress a seller enough for them to accept your offer instead of your competitor's, even if their purchase offer is slightly higher.
Since large deposits do impress sellers, you may discover that with a large deposit you may be able to convince the seller into accepting a lower offer. More money up front could mean saving you money later.
The Closing Date
An absolute necessity in your offer is to provide a closing date. This way both you and the seller can make plans to move, and the seller can make plans for buying his or her next home. Most transactions do close on the right date, but do not be so inflexible that a delay creates insurmountable problems.
For example, if you are currently renting and need to give the landlord notice of you move, you may want to allow a little flexibility. Otherwise, if your closing occurs a few days late you could find yourself staying in a motel with your belongings packed somewhere while you pay for storage costs.
There are also times when closing can be delayed for weeks, through no fault of your own. Make sure you have a back-up plan prepared for such a contingency.
Transfer of Possession
Once the deeds have been recorded, the transaction is considered "closed." This is when you take ownership of the home. However, it is not always possible for you to occupy it immediately. There can be several reasons for this, but the most common is that the seller may be purchasing a home, too. Usually, their purchase is scheduled to close simultaneously with your purchase of their home, but situations may arise.
As a result, it is customary to allow the seller a couple days (three days is a good number) to turn over actual possession and keys to the home.