The first step to building your coffee table is to glue up panels for the top shelf, bottom shelf and optional middle shelf, if one is desired. The top shelf will have a section cut out later to accommodate the beveled glass top.
Begin by gluing up two 5-foot long pieces of 1x8 with a 5-foot long 1x6 sandwiched in-between. If you have access to a jointer, it would be best to joint each edge before laying them out for biscuits, to ensure a clean joint. If a jointer is not available, you can clean up one of the edges with a long straight-edge and your circular saw, then use your table saw to cut the opposite, parallel edge.
Lay out the three boards so that their grains match well, preferably with each board's end grain arcing in the opposite direction of the next board to prevent bowing. Make some pencil marks about every 6-8 inches on each board along the joints for biscuits.
Then, cut slots for the biscuits using your biscuit joiner. Apply a small amount of glue in each slot and insert a #10 biscuit. Apply glue in the opposite slot, as well as a very thin layer along the edge of the board, and assemble the joint. Remove any glue that squeezes out immediately with a damp cloth to avoid any finishing problems later.
Once both joints have been assembled, clamp the assembly using some large clamps. Simply snug the joint with the clamps - do not over-tighten the clamps so that all of the glue is pushed out of the joint.
Set the assembly aside to dry and complete the second assembly, as well as the third if a middle shelf is desired.
If one of the ends is uneven, you can use a straight-edge or a Panel Cutting Jig to square it up when the glue has dried.