Leave ceiling rafters exposed. They're one of the most instantly recognizable features of a loft. Paint or stain them if they're a little too unfinished for your taste.
Juxtapose sleek, modern lighting touches against the unfinished rafters. Use monorail, track or cable lighting for a dramatic touch that works well as general lighting for an open loft. Give each area its own fixtures, to help divide the space without physically partitioning it.
Stain concrete floors to create a solid wash of color or a marbled or leathery faux finish. Tape off thin "grout lines" before you apply the stain if you desire a tile effect. Paint, polish or leave the concrete as it is, to emphasize that the space is a basement. Alternately, install a light hardwood or laminate floor to play against the rawness of the unfinished rafters for a sleeker, more finished result.
Drywall exterior cement or concrete walls to add variety to surface textures and keep the basement from feeling too hard and cold. Pay homage to the traditional unfinished industrial loft wall by leaving a section unfinished. Use the unfinished section as a visual space divider.
Install sliding wall panels that glide along a track, much like sliding closet doors, to physically divide and alter the common areas. Install lit panels along walls to give the illusion of daylight.
Paint some or all of the existing support structures, such as poles and beams. Make them pop with bright, unexpected colors, or even decorative painting, to enliven and contrast the basement's dull and neutral unfinished surfaces.