If you're able to, put 20% down. This helped me avoid getting into a bidding war, and of course, saved me the expense of PMI. Also, once you close escrow, be sure to file for tax credits that may apply to you as soon as possible.
Depending on where you are looking to buy, you may have to put in a bid as soon as you are finished seeing a place that you like in order to have a chance. Thus, it pays to have done all your homework in advance about an area so you will be able to jump on it.
Stay away from short sales unless your agent is super skilled in such matters. I've heard some horror stories!
Keep a positive attitude, and good luck! The process is stressful, but sooooo worth it!
