Start w/ a valve adjustment, new plugs, rotor, distributor cap, and OEM plug wires. Make sure your injectors are flowing to spec; if not replace w/ new ones. Add a K&N air cleaner, a new Honda fuel filter, change your coolant (Honda OEM only) and thermostat, and use the best quality oil (Valvoline, Castrol) and a Honda oil filter.

Next thing would be to make sure your cat is not plugged (get a smog check) and eventually replace w/ an aftermarket hi-po one. Add a cat back exhaust - ask for recommendations re: aftermarket brands, or have a local shop fab you one using a quality low-restriction muffler and make sure you retain a resonator in the system (or it'll sound like a 2-stroke dirtbike). Lastly, add a quality header (DC Sports), and possibly a short ram intake (but don't expect much improvement from the intake if you've already got a K&N filter - if you intend to get an intake anyway, make sure it comes w/ a K&N filter, and get either an AEM or other quality one, as the eBay ones typically come w/ junk filters. (some will disagree w/ me re: not using a cheapo eBay intake, but if you're not a seasoned gear head, play it safe and buy trusted brands. . .just my opinion) Avoid getting talked into a cold air intake, and stay w/ a short ram type (much easier to install, and no worry re: deep water lunching your engine due to hydrolocking).