Last year I rebuilt my drive train, I just bought what I needed and what I could afford until it was all put right. It was all Shimano except for an FSA crankset. Now I know I will need to do it again eventually and would like to buy some pieces as I go, but I am always reading here people asking if X Shimano component is compatable with Y Campag set up. I am quite happy with the notion that you should pick one maker and try to get all your components to fit together.
I also often see bike reviews saying the frame is such and such but it ONLY comes with Shimano Sora, or it comes with top of the range Sram Red. So my question is how do you know what level of components/set is worth while? How do the different names from each manufacturer match up? At the moment the only think I have got to go on is the price, persuming that more expensive 'should' be better and new components are better then old worn ones.