Following a pattern
Are you using a plastic, melamine, bakelite, etc. pattern, or are you talking about a paper pattern that is glued to the work piece? If the latter, then as said you can sand to the pattern. If the former, then what you need is a "pattern bit," which is a router bit with a bearing that follows the side edge of the pattern, allowing the bit to create the same contour. One word of caution: make sure that you're within about a sixteenth of an inch of the pattern's edge before you use this bit to avoid loading down the router and/or creating a lot of tearing. Also it helps (sometimes) to use a climb cut, but be very careful with that.
~ Peter