Remember that scene in Mallrats where Brodie is thumbing through some comics being sold at the strip mall and indignantly exclaims, "You should have boards in these. BLOODY SAVAGE!" It's a funny line, and one that people who collect comics should take to heart. While you should always read comics for the pure joy of it, you should also take measures to protect your collection--and this process should begin as you purchase them. In all likelihood your comic book collection isn't likely to pave an easy path to an early retirement, but some comics do manage to increase dramatically in value and should be protected. With fewer printed comics being sold these days than in the glory days of years past, and comic properties being snatched up by movie production companies like never before, modern comics are definitely a collectible commodity.
Taking care of your comics starts in the comic shop before you even purchase them. Make sure your hands are fairly clean. Dirt, your own sweat, and bodily oils can damage paper products. Look an issue of the title you want to read in the best possible condition right from the start. Comics get roughed up during shipping. The issues on the shelf of your LCS (local comic shop) will likely be in various states of being. If you can, avoid new comics which already have wear on the spine, corners, or other more obvious flaws like rips or printing errors.
If you can afford to, always buy bags and backing boards! Bags and boards are extremely inexpensive, and are your first line of defense to keep your comics in pristine condition while transporting them. Insert your new comics into bags with backing boards before you even leave the shop. Check with your LCS to be sure that their bags and boards are acid free. It makes no sense to try to protect your comics with bags and boards which could ultimately cause them harm. This will give them a better chance to remain safe from things like raindrops, pushy commuters on the subway, or having the corners damaged while shifting around in a car ride home. If the any of the comics you bought happen to be poly-bagged to keep the story a secret, know that these bags are not meant to protect your comics over time. Poly-bagged issues should be opened, bagged and boarded, then reinserted into the bag. Take these early steps from the very beginning to assure that your beloved comics remain in mint condition.