We could likely have started lower, and we messed it up by using some repairs that needed to be done (that were clearly priced into the advertised price) as an argument for dropping the price when we ought to have been able to get that price drop and make the offer contingent on the seller having some of the repairs done on their dime.
The key thing is to be able to move quickly. They picked us because the alternative would have been to wait for other offers, while we turned around and started negotiating as soon as we were sure, offer an agreement in principle subject to a survey right off the bat if they could meet our price, had an agreement in principle from my bank, and had been renting so we stressed that we could move on everything immediately.
If you can stress to the sellers estate agent in particular that you can move quickly, keep in mind that it will be in their interest to get a quick, trouble free sale vs. hanging on for weeks for 10% more commission, and that will influence how they deal with their client (conversely, it is in your interest whether selling or buying to be very wary when an estate agent pushes you to accept an offer - there's been some survey where it turned out estate agents typically hold out longer and sell for more when selling their own houses than their clients do).
* Price we were willing to pay "out the door" (a hard, absolute max that wouldn't leave us in dire straits if one of us lost our job) * How much work we were willing to do after the sale * Tied in with the above, a minimum 1-year, preferably 2-year warranty on major repairs paid for by the seller * Within a 30 minute rush-hour commute to the furthest employer * 30-year mortgage that we can afford to pay off in 15 years * Any school district except the worst few in the area (no kids yet, but this is our first home and we'll have it 5-10 years; when we move kids will be just entering the equation and we need to plan that we may not be willing or able to move)
As with any negotiation, the most important thing is knowing exactly what you need, what you want, and what you can (and will) spend. The hardest part (for me anyway) is getting a deal that is everything I need, most of what I want but is 2% more expensive than my max and still being willing to walk away.
The main principles of negotiation (take your time, set yourself a price and if you can't get it for that price walk) apply. But there may be a scarcity of offerings that suit you, a place may have extra perks (location near water / the beach) and so on.
The most important facts about buying a house are how long it has been on the market and what it was bought for. If you can't figure out the latter you may be able to make stab at it by comparing the market development relative to when the house changed hands last and what was done to improve it since.
Happy house hunting!
Silicon Valley is a very, very hard place to buy a house right now -- inventory is crazy low.