Found a house you are hoping to buy? If so, you are probably eager to tell that to the seller and move forward toward a signed purchase contract. How exactly to take the first step, however, depends in part on which state you live in.
In some states, the standard home-purchase offer is a bare-bones statement that "I'll take the house for $X." After that. the seller writes up the first actual draft of the purchase contract. The buyer reviews the draft and could potentially either sign it on the spot or negotiate for amendments before signing.
In other states (the majority of states, in fact), your offer must be a written document that you've signed and that is so complete that the seller could then sign it and create a binding contract right there. Or (as is more likely) the seller could counteroffer by filling out the same form with slightly different terms and sending that to you for possible signing.
Unless you're in a state where it's the seller's lawyer who draws up the first draft of the contract, you're going to want to use the same basic form as all other home buyers. That form is most likely going to be available from your state's Realtor's association. Your agent, if you have one (and now would be a very good time to sign up with one) can get the form for you or, more likely, prepare it on his or her proprietary software program.
If you don't yet have an agent, be wary of the seller's agent trying to convince you that, "Don't worry, I can draw up all the paperwork on your behalf." That's called "dual agency," and it leaves you without someone whose primary loyalty is to represent your interests.
Remember that signing a contract isn't the end of the negotiating you might be doing with the home seller. During the escrow process, as the home inspection or title search possibly turn up issues with the property, there's a good chance you'll need to negotiate for price adjustments, repairs, changes to the closing date, and so on. It helps to have someone looking out for you, and only you, during this time.
Most contracts include basic information such as names and the property address, the price that you are offering, a proposed date for closing, and contingencies--events that must happen within a certain amount of time (such as 30 days) in order for the deal to become final. For example, you might want to make your offer contingent on your qualifying for financing, the house's passing certain physical inspections (see Getting a Home Inspection), or your ability to sell your existing house first.
One big reason that the seller is likely to counteroffer is so as to add pro-seller contingencies to the offer, such as a condition that he or she have found another house to buy before closing the sale to you.
For more information on your options when it comes to contingencies, see Contingencies to Include in Your House Purchase Contract.
Don't make the mistake of thinking that as soon as you offer to buy the house, it's basically a done deal--even if the seller says, "Sure, great." Only after both parties have actually signed onto the purchase contract are you each obligated to follow through. Once that contract is signed, you are "in escrow," and bound to continue on toward the closing unless one of the contingencies isn't met.
For a detailed analysis of issues like how to decide the right price for a house, how craft an offer tailor-made to your and the seller's needs and interests, and how to negotiate the final contract, see Nolo's Essential Guide to Buying Your First Home, by Ilona Bray, Ann O'Connell, and Marcia Stewart.