Most will say to use lump. Experiment with different brands of charcoal and see which you like best. You should also try to avoid using too much green wood for smoking if possible. Dry or seasoned wood is best.
The Rancher is good stuff if you can find it in your area. I am a big lump user (don't tell the stickburners, but it's wood too), however the 100% all natural briquettes like Rancher and WGC are truly the best of both worlds in a bullet type smoker.
Green wood smokes but not as good a smoke. It's about 60% water and doesn't give you as much heat either. There are some peple that like grren wood and there will be arguements forever about which is best. There are rumors (I have seen no scientific proof) that it gives off more Creosol.