In our studio workshop someone had built a large assembly table, that was missing a lot of little things to make it a good workbench. So I set about making some essential modifications, that could help in your own workshop.
First, the sides were vertical 2x6's. This made it almost impossible to clamp anything to the table top, except by using very large clamps. I simply used PL Premium construction adhesive and long screws to add a 2x2 lip along the long sides of the bench. If you install them just a bit high, then plane them down flush and flat to the table, you now have a good clamping edge.
A bench this size can get in the way in a shop, so we added lockable wheels. Make sure you get wheels that are rated for the weight you will be putting on them, and shorten the legs accordingly so that the work height remains appropriate for your height.
No workbench is complete without at least one woodworking vise on the end. The best basic vise is probably the Record Marples quick release vise. With just a squeeze of the quick release handle you can slide it in or out, and then just crank a turn or two to tighten it up. Make sure that your vice has a raisable dog built into it. This works together with dogs in the workbench. Dogs can be fancy, like the Lee Valley spring loaded brass ones we have, or simple dowels with a flattened side sticking out of the bench. Generally screw and glue a 2x4 to the underside of the bench where you want to drill the dog holes, so that they are firmly supported, and drill the holes all the way through so that sawdust will fall through. You can put a wire under the bench running the row of dogs right down the centre of the holes to keep the dogs from falling through, but letting the sawdust through.
How far apart do you drill the dog holes? Start by facing the vise with 3/4 inch plywood or hardwood. Then measure the widest opening you can have of the vise. Space the dogs just a little less than this opening, as that is the travel available to make sure that you can actually clamp any length of board onto the table top between the vise dog and the table dog.
Scraping a work table top is a regular maintenance job that you must do. This keeps glue drops from scratching good surfaces, or paint blobs from staining a new project.