If you buy an older home and the seller offers any type of allowance, just take that right off the asking price. Nothing like paying off $1,500 for new carpet over 15 or 30 years.
Low ball the crap out of your first offer. The sellers will usually respond right away with a counter offer, wait a day or two and go $2,000 higher than your first offer. It helps to look up what the property was last listed/sold for when doing this as well. Also Google the owners and see if you can find out why they're selling. Anything being sold as part of an estate is ripe for getting below market value.