Restore to factory settings last resort help. iPhone

Bb. ee. Addressd here. I am having lots of crashes, slow response, typing slowness, etc. I think itbmay be related to my 12 or so apps installed. At this point li seriously wanna get my phone back to its factory settings as itnhas just come outbof the box formthe first time. No restoring backup etc. You get it. I want a clean slate so I can be VERY discriminate about whatno install after I getbthis out box fresh start. Please please explain to me the best way to getbthis back to fresh off the assembly line condition, preserving nothing. Thank you all in advance and bless all your help and patience.
Message was edited by: Applewiz
2.4 Alum 24in iMac 4GB Ram, 13" 2.4 Alum Macbook, - 12" Powerbook 1.5 Ghz, 1.25GB Ram Mac OS X (10.5)