Basements are usually cool year-round—comfortably so in summer, a bit chilly in winter. Basements are often partially insulated by the ground around them, so your existing heating system should provide the moderate amount of heat needed for comfortable temperatures. It's always a good idea, though, to make your basement even more energy-efficient by wrapping walls in insulation with R-10 to R-19 values.
Your current cooling system probably does a sufficient job of keeping the basement comfortable during the hottest summer days. If you're having difficulty keeping a walk-out basement cool in summer, consult a heating and cooling contractor to determine whether you need a more powerful cooling system. You also could consider supplementing the current system with a window air-conditioner.
Many basements in homes cooled and heated by forced air already have the ductwork necessary to distribute the warmed or cooled air. If not, a technician can install ductwork relatively simply and inexpensively because a furnace is usually located on the lower level. Still, your basement may need a supplemental heat source. If you have a walk-out basement with large, unshaded, south-facing windows, you may need supplemental cooling as well.