* as sss has said, check your timing
* check your spark plugs
* give the throttle a good clean out with carby cleaner or similar
* check your distributor rotor and cap to see that the contact points are good
* check your leads with a multimeter to see that the impedance is within an acceptable range
or if its more of improving performance over standard, then you could try:
* high flow air filter
* performance chip
* exhaust (inc extractors)
* aggressive camshaft