I'd like to remind everyone that there's plenty of basic troubleshooting information right here on SDN. I've seen quite a few "somethings wrong, what can I do now" questions recently.
I suppose we are all here to share our experience and learn more about the Enterprise Portal and its operation. To that end your education is best served if you do some background work first, before asking a generic question, so that the community can benefit from specific problem solving discussions rather than generic how-to basics.
Those basics are well covered already.
Why not start off here:
https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sapportals.km.docs/documents/a1-8-4/troubleshooting ep 60 sp2.evn
And always use:
http://help.sap.com/portals/index.htm for EP6 SP2
or:
http://help.sap.com/nw4/ for NetWeaver EP6 SP3
And just to refresh your memory, here's where it all begins for EP6 at SDN:
https://www.sdn.sap.com/sdn/developerareas/ep.sdn?page=getStart_ep.htm
Keep those cards and letters coming!
Nick