Where do a novice do to make it run faster?

So, it is time to improve performance, it is running to slow.
AFAIK (as a novice) there are a few general areas:

1) hardware
2) rewriting my queries and table structures
3) using more predefined queries
4) tweek parameters in the db conf files

Of these points:
1) is nothing I can do about right now, but in the future perhaps.
2) will be quite hard right now since there is more code than time.
3) almost like 2 but perhaps more do-able with the current constraints.
4) This seems to be the easiest one to start with...

So what should I do/read concerning point 4?
If you have other good suggestions  I'd be very interested in that.

Thank you :-)