There are lots of websites on the net dedicated to SOHC vtec...just go to google and do the search.
But for the meantime, what you can do is:-
(a) change to open pod air filter;
(b) change your extractor and exhaust system;
(c) change spark plugs and plug cables.
I really dunno which brand should you choose for (b) and (c) cos I never upgraded my SOHC engine. But these are the things that people would do 1st.
Apart from that you might wanna look into using a lightened flywheel and a slightly bigger throttle body...
If you're really serious in upgrading SOHC, like Shiro said, it ain't gonna be cheap. Most of the SOHC guys on the net or in HondaTuning Magazine even upgraded their pistons etc etc. When you are about to reach this level you might want to rethink whether to go that far or just plonk in a B series. Main thing is to ask yourself what's your budget and how far you wanna take your SOHC. Reading magazines is a good place to start with...