1) Get pre-approved for a mortgage before you make an offer.
When you are trying to buy a house in a competitive market, your offer to purchase should contain as few conditions as possible. An offer that is conditional on obtaining financing is often a deal killer. The seller may accept a competing offer for less money rather than take the risk that you won't be able to raise mortgage money. A pre-approval letter from your lender tells the seller you are ready and able to commit.
2) Know when to quit.
When you act on emotion, rather than reason, you may end up paying too much money. This can happen when you fall in love with a particular house and start fantasizing about how great it will be to live there. Another reason you may be driven to pay too much is that a bidding war triggers your competitive instincts and you must buy the house at all costs - which you will regret later.
3) Set enough money aside to cover closing costs without having to forgo eating for a couple of months.
You've put together a down payment. Be aware that there is also a long list of expenses you may have to pay at closing, depending on where you live and who your lender is. Closing costs can add up so get your real estate agent to compile a list of other expenses.
4) Coordinate the date you take possession and your moving date.
If possible, avoid a situation where you've got to camp out with relatives or find a short-term rental because you must vacate your old house or apartment before you can move into your new digs. Moving once is enough.
5) Insist on a home inspection.
The first really cold day you spend in your new house is way too late to find out that the furnace doesn't work. The one condition you should always include in an offer to purchase is a home inspection. Find out how much it will cost to fix any defects and have the seller fix them before you agree to buy or deduct the estimated cost from the final price you offer. If the seller won't help bear the costs, and you want to go ahead with the purchase, make sure you can afford the necessary repairs on top of your mortgage.