Depends on what kind of coins. If they are common dates in circulated condition, use a grading guide ( ANA or Photo Grade as they have great pictures of each grade condition) and then use a Coin Values or Red book to determine retail value. Coins that are polished or damaged need to be "net graded" down the scale depending on severity. If you have any coins that show a significant jump to the grade just above, are in a great state of preservation (having significant amount to full mint luster) or are of a better date or variety...take to a reputable dealer. A fair dealer will give you 60% and up of retail value, on common stuff, and as much as 90% on better coins he won't have to sit on till sold again. One thing to prepare for is common and significantly worn Walkers (less than VF), Mercs (less than EF) and more recent silver, bring melt plus a small percentage. Worn out (non full rim), common date Barber stuff brings a small premium above that. I know this doesn't seem right but...Barber coinage was heavily used, very little premium coins are left, and tons of worn ones are.
Don't clean the coins, post pic's if you have something good and sell locally. Hope this helps.