Two things come to ming:
1. Subtle is better than 'in-your-face'. Consider dry-brushing for instance. It's probably more 'realistic' to dry brush your model in a lighter shade of the base coat than 'silver'. My suggestion is to always do things with subtlety first, and then increase the effect until you get what you want. Going 'too much' right at the start gives lots of 'impact', but rarely is 'realistic.
2. Practice your techniques one or two at a time. Another poster suggested getting some smaller models to practice on. I agree with this and am currently doing this myself. I'll get a small (1/72) common armor kit that is relatively simple to assemble, and then I practice my weathering/painting skiills on it. In the end I get a pretty good little model that goes on my shelf, but I don't feel too bad if it's not 'perfect'.
Nice to see the younger guys in the hobby. Stay with it!!
M.