I just got the griffon games decals, and stupidly enough I don't know how to get them off an apply them. Any help would be appreciated.
Make sure you have a gloss varnish on the area you are applying decals too. They'll sit better.

Get a bowl of clean water (filtered hopefully)
Tweezers (self closing perferred)
Old paintbrush
small siccors or xacto

Trim the decal you want close to the actual decal leaving a paper handle for the tweezers. If your decals are pre-seperated you'll need to score the paper between the "handle" and decal.

Grab the decal by the handle and dunk in the water for 30-60s

position the decal over the area you want it. Use the paintbrush to gently brush the decal off the paper. Pull the paper away as you do this.

Use the brush to position the decal. Dont be afraid to add a drop of water to help float it where it needs to go. Once in place dry the brush, and use it to wick away extra water.

Set the model aside to let dry and clear coat once dry.
See, now this is stuff I love reading about on the forums. I am never good at decals. So this is very useful to me.

Do you have any tips on painting extremely fine lines? I am trying to paint my shadow ships and I want to do the veins that you see on the hulls.
There is a way to cheat with the veins on shadow ships. Run your hand over the model, and you will notice that it is not smooth. What you do is undercoat it black, then drybrush it with greys or metallic silvers which pick up all the raised portions, making it look like you've painted all the veins.
I've found that the GW Rough cote paint makes a great basecoat, sprayed over black and then lightly drybrushed gives the model a fabulous texture.