I've been playing for about 6 years now but only about 2 seriously. I decided a couple of months ago to get serious and learn theory and proper technique.

I've been doing great memorizing the fretboard and learning scales and such. And I'm working on finger strength and different picking techniques.

But I find my self getting hung up sometimes because in some situations I can't figure out which fingers to use.

Sometimes it's obvious which finger to hammer or pull with and sometimes it's obvious which fingers to use when playing a scale.

Other times I have no idea what the "right" thing to do is. I think this is the biggest thing preventing me from progressing further.

What are the rules that I should be following?

Are there any good lessons or sites?