When it comes to Eisenhower dollars, specimens that are in mint condition are typically the most valuable. A coin in fine condition is usually worth much more than a coin with scratches or marks. It is also important to realize that value is not determined by age alone. Of course age and rarity make a coin more valuable to collectors, but they aren't the only factors that matter. Demand is a key factor in the market value of any collectible coin.
Whenever possible avoid handling your coins. When collectible coins are handled you run the risk of them being nicked, scratched, or dirty and their value is lessened. When it's absolutely necessary you should hold them on the edges.
Coin cleaning, which is not recommended, should be done only by an expert, and only when absolutely necessary. Removing the patina that develops on an old coin could also decrease its value, as collectors might prefer coins with this evidence of age.
Most holders provide adequate protection for Eisenhower dollars but you will want to be sure that your most valuable coins are protected not only from fingerprints and dust, but also moisture. Aside from the typical stapled or taped packets that provide average protection, there are other protectors out there that can do a better job and guard against moisture as well. In any case, it is best to store collectible coins in a dry place; never store them in a basement or other cool, damp area.