mcunha you are set! don’t worry about the clothes, model him with the clothes on!!! Unless you intend for him to disrobe, there is absolutely no reason to model the character without clothes. Download Sintel Lite from Ben Dansie’s Thread and look at how she is constructed. I haven’t done that yet myself, but I am betting there is nothing under the clothes. So really you have already done the hard part, just setup your background images and go to town. You will not recognize your character until he is complete.
Start with the head. I have linked to Jonathon Williamson’s face tutorial on Blender Cookie too many times, the mods will think I am a spambot: http://www.blendercookie.com/2009/01/09/modeling-a-human-head-series-part-1/ Model the loops and massage them slowly, build your character logically and bit by bit. Look at my Train Toon’s Thread and see the steps I take to create the characters.
Your model sheet is top notch. If you setup your background properly and slowly match your reference step by step, piece by piece in all three views, how can you go wrong. Trust me your work is done already. If you are struggling with edge flow and topology, simple stuff like pushing verts around, then you just need some practice. You do not need toes… you need to model those pants drooping just like you drew them abd the shoes under them, but adding your artist’s eye to accentuate the details you have already laid out so well. Don’t try to correct your drawing with 3d though, correct the drawing.
If you need modeling technique, just start at the beginning of blendercookie’s tutorials and watch them all. You don’t really need to actually perform the tasks described, of course when something interests you, try it out. You just need to sit there and absorb the talent and the mindsets of these skilled artists. Jonathon has done the world a great service by sharing his knowledge, as have the others at the cookie. Munch, munch munch! Citizen is well worth the money, and you should really order the kara tut and work through it if you haven’t already.
Of course I have written this to you assuming you are serious about learning 3d, not just blender, but 3d in general. http://blendergroupie.blip.tv/ -Don’t just watch this. Buy the dvd’s Ton needs and deserves your money as much as the next man.
Well I hope this helps, you may know all this already, and I may be preaching to the choir.
Edit: Looking closer at the sheet, yes you need to redraw it. Damn that side view, it is so hard :).