A template means never having to say "Oops"
Let's say you want to make four table legs with matching curves. A table-mounted router and template enable you to produce as many identical legs as you want.
Using 1/4" hardboard or medium-density fiberboard, make a template to the shape you want. Use a bandsaw or scrollsaw to cut close to the line on the template, then sand to it. Attach the template to your stock with cloth-backed, double-faced tape, orienting the grain for best effect. Bandsaw the workpiece within 1/8" of the template.
Turning to your router table, you have two choices for router bits--a flush-trim bit and a pattern-cutting bit. In some situations, you might need both.
A flush-trim bit has a ball-bearing pilot mounted at the tip, as shown in photo. To use this type of bit, place your workpiece on the table with the template on top. Adjust the bit height so the pilot runs along the template's edge.
On pattern-cutting bits, the pilot sits between the shank and the cutter, as shown in the illustrations. Your template rests on the table.
Whichever bit you use, ease the workpiece into the bit until it contacts the pilot, then move the piece from right to left. If you've left more than 1/8" of excess material in some spots, trim it to size with a couple of shallow passes. Don't pause too long in any spot, or you'll burn the wood. Double-check the surfaces you've just routed before you remove the template. Sometimes another pass will smooth out a rough spot. Finally, slide a putty knife blade between workpiece and template, pop them apart, remove the tape, and you're done.
When you have a workpiece that's thicker than the cutting length of your bit, use a pattern-cutting bit and a flush-trim bit in the sequence shown in Steps 1, 2, and 3. Make one pass with the pattern-cutting bit, template side down. Remove the template, then make another pass with the pilot bearing riding on the surface you just machined. Finally, flip the workpiece over and use the flush-trim bit, with the pilot bearing riding on the previously milled surface.