I just take the really big ones off that are shading buds below them. Ones near the tops that are shading buds I just cut the ends of the leaves off to expose the shaded buds to light, like about the outer half of the leaflets usually. Better to leave half of a leaf than to take the whole thing off if it's near the top. The ones in the middle or bottom pretty much have to go completely because they're not getting enough light anyway and usually start dying off before long so might as well speed it up a little and reduce water usage.
Near ripening time I do take most leaves off so all the buds get good light, just leaving the smaller leaves near the tips, or else the lower buds won't thicken up enough. It also makes harvesting easier because you already got rid of a bunch of the worthless leaf already so you don't have a big pile of it all at once. I try not to take much leaf off until buds are well developed though, not in early flowering. You need a good amount of leaf for solid buds to set up. I found that if you take a bunch of leaf off in early flowering the plant will just replace them by making the leaves at the base of the buds get bigger than usual, so you're really just slowing them down because they have to put energy into growing those bud leaves big to replace the fan leaves you removed. In late flowering they don't bother growing the bud leaves big to make up because the big leaves start dying by themselves anyway so they apparently don't even need them anymore.
