BuyDomains is pretty good to deal with. They are a buy and sell domain company, not buy and hold.

Just make an offer on the low side of reasonable. (recent sales: http://dnjournal.com/domainsales.htm).

If I was prepared to pay $2K for a domain, I would start with an offer in the $800-$1.2 range.

If they have a fixed price, don't be afraid to offer 50% of their asking price.