First of all, if you don't have a service/repair manual (Hayne's, Chilton, etc) I highly recommend investing in one. It makes things a lot easier, plus they usually have a troubleshooting section that might point you in the right direction.
The quick and easy things to do are check for vacuum leaks and a dirty/sticky EGR valve or IAC valve. It's an older car with (I'm assuming) old hoses, so maybe they have worn and developed a crack or hole. You can also try cleaning out the throttle body.
Also check the coolant temp sensor. These can go bad and cause problems.
Other things to consider are the TPS, fuel delivery (fuel filter, fuel pump), air filter, oxygen sensor(s), etc. I'd suggest trying the other things first (vacuum lines, EGR & IAC valves, and coolant temp sensor) before getting into these.
Good luck!