Never, ever clean, dip, polish, scrub or in any way attempt to clean your coins
. This will greatly reduce the value and may make the coin worthless.
Do not open any plastic cases or coins sealed in clear envelopes. Bring any boxes, envelopes or slip cases the coins may have come in.
Sort coins by type and denomination. For example, sorting all of your Lincoln Wheat Pennies, Mercury Dimes, etc. into separate bags or containers speeds the process.