Start with cleaning the carb. Remove and clean all of the jets, choke assembly and air screw (the air screw should normally be at 1/2 to 2 turns out), pay close attention to the pilot jet, air screw and the choke assembly as these three work together for a good clean idle and good low end throttle response.
Check all passages looking for debris. The best thing to do is use plenty of carb cleaner (from a spray can) forcing the cleaner through each of the passages. Don't forget to check and clean vent hoses. Replace hoses if needed.
While the carb is off check the intake reeds for cracking or fraying. Replace if needed.
Check compression. If compression is above 130 PSI your good. Anything below 120 PSI you need to consider at least a new set of rings. (I'm sure I'll get some commnets about those numbers but they are a good starting point.) The 200 is real sensitve to good compression where the bigger bores, especially the 300, are less sensitve.
A good habit to get into is to check compression after doing a top-end to get a reference point. A lot of compression gauges are not real accurate to exact PSI but they are accurate to compare to themselves as a starting point. Write down your fresh top-end PSI and compare it to later compression tests and when it drops down to 20% loss, its time to freshen up the top end. Only check compression after you've run about a half tank of gas as the rings need to break in.
Check for excessive slack in the throttle cable.