Im not an expert but have done a few single speed conversions, First remove the shifters and shifter cables, both fd and the rd, then take the bike down to the LBS and have them slap a free wheel cog on the rear wheel, while your at the bike shop get yourself a front chainring single speed adaptor kit (about 5 bucks) its just a bunch of small nuts n bolts that will take the place of the ones you remove from your front chainrings, most times you can place the smaller chainring where the big one used to be, then use the nuts n bolts from the kit to attach the smaller chainring, you cant use the old ones cause theyre to long, sometimes the rear wheel needs to be dished out a bit so the chain can line up with the front chainring, if you know how to do this yourself your ahead of the game add a chain and thats about it I keep both the front and rear brakes as long as they are functional the rest is up to your personal preferance Im sure if I missed something someone will be nice enough to tell you any other questions feel free to ask heres a pic of my latest conversion =)