First and foremost: DON'T THROW ANYTHING AWAY!  The old adage remains true: "One person's junk is another's treasure."  Let the professionals decide what to keep and sell, or what to discard.
 

Don't assume that your personal property is not valuable enough for an estate sale.  There can be very good money in mundane household effects, non-collectible furniture, daily dishware and silverware, garage tools, etc.  Again, let us take a look and decide what our experience tells us your property will bring.
 

Don't do a garage sale yourself to "prepare" for the estate sale.  While it's true you will not have to pay yourself a commission, you will probably also not price items in accordance with the market.  Underpricing items obviously wastes money, and overpricing causes things NOT to sell.  The professionals pay for themselves in many cases by using years of experience to properly price your property.
 

DO check out your prospective estate professional.  "All estate liquidators charge about the same commission, so they are all probably the same."  Not true.  Trust, reputation and integrity are very important in a cash business dealing with untitled items of personal property that are easy to make "disappear".  Check the credentials, background, and references of the estate liquidators you are considering.  Find out if they take credit cards (many do not; we do - it increases sales and creates even more of a paper trail, with which we have no problem). Ask for a copy of their bonding and verify the amount. Finally, ask how long they have been doing this, and how many sales they conduct per year.
 

A word about auctions versus "tag" sales.  The general rule is, a "tag" sale (estate sale where all items in the home are priced - this is what we do) usually generates more revenue for the client in a big metropolitan area.  There are exceptions, and sometimes a combination of auction and tag sale will make the most sense.  We will counsel with you concerning the options that will maximize revenue in your particular situation.
 

Finally, don't assume we will just discard or donate items of some value at the end of the sale.  We frequently store unsold items on a consignment basis for our clients (we have climate controlled, fully insured and alarmed storage), and take them to other sales.  Rest assured, we will not take a 2-year old leather sofa in perfect condition and donate it to charity or give it away. This is one of the reasons we have our own moving van.