ok first decide wut u wanna do... have some references and examples on hand.....
then go 'File>New' ...
choose your canvas size.... this can always be changed after...
and resolution...: bigger is better.. it can always be lowered later
then choose if you want the 'base colour' to be transparent, white, or black..
then show off your artistic and design skills and make urself a banner!!
ok that must not have been much help.... um.... well usually if i'm stuck, I pick something that i really like and use that as a 'reference' If you plan to base your banner on a person... thing...etc (ie. Edison Chen), then have a couple images of that thing (Edison Chen), I say a couple cuz eventually u'll probaly change your mind about sumthing, and u'll want to have it on hand.. pick your favourite, and put it in..... then u'll probably want to erase the background of it. .. then make your own background .. On a different layer (so you can make changes later)... add filters, text, and voila! you have yourself a banner!
Tipz: if you're working on something big, like CG, or a skin, etc. make sure to save as.. constantly as u work, with different names (eg. skin1.psd, skin2.psd...etc)
if that wuz totally useless and pointless and didn't help at all =P... u can check out these sites:
http://myjanee.home.insightbb.com/tutorials.htmhttp://www.stickysauce.com/tutorials/photoshop/basics.htm