If camping at a commercial campground, bring your own wood or buy some at the camp store. Note that in many states, it is not legal to transport firewood across state lines into that state. It is sometimes not legal to transport firewood from one part of the same state into another part. This is an effort to control the spread of invasive insects such as the emerald ash borer, Asian longhorn beetle, etc. These are important laws to respect and obey.
At a campground, do not gather firewood from the surrounding forest! Most campgrounds have rules against this, and it is not so they can sell you expensive wood. In a heavily camped area, the forest simply cannot sustain that level of use. Rule breakers will already have depleted enough of the forest - don't add to their sins!
If there was already a fire ring present, if it is allowed, and you are in the wilderness, gather firewood well away from the campsite. Do not cut down any trees, live or dead. Dead trees are an important habitat for many forest creatures. Instead, look for fallen limbs that are not lying in full contact with the ground and use those. Wood that is lying fully on the ground will likely be too wet to use as firewood.
