When trying to get the best (highest) price for your listing or trying to get the best (lowest) price for your purchase, there are some things to avoid.   Lets begin with ---this is a business decision, not an emotional one! If someone gives you a lowball offer on your home, dont get upset, counter with the right amount and see where it goes.  Sellers often take it personally and decide not to counter----bad idea.   The buyer could be unemotional and not wanting to leave anything on the table--it costs nothing to counter back and let it go where it goes.  Example:  I have had a buyer come up $20K in the 2nd offer to then purchase the home. Next, know the amount that you will take and be prepared to go there--if a buyer offers the amount you decided to take, seal the deal and breathe a sigh of relief--showings are over and you can begin the process of moving ahead.   I have seen sellers want to wait on the next offer to see if they can make a little more on the sale---bad idea.   Take the right amount when it comes and be happy you got it.  Finally, think hard before walking away from a deal over $1-2,000., does that make sense?  How much will that affect your overall deal, whether it is payments on a mortgage or $ in the bank?   Remember to weigh everything and don't lose sight of your goal. 
Happy Negotiating!