When the bite is tough, some suggest dropping down your line test/diameter. What is a general rule for how far you go? For example if I fish mono in 12 lb .013 diameter line do I drop to 8 lb .011? Is that enough or do you go to mono or fluorocarbon lines where 8 lb test is .009 diameter?

If you want to reduce line diameter consider PowerPro braided line. Ten pound test line has the same diameter as two pound test monofilament, and it has other advantages as well.

I switched the leader on my fly line to 8lb flouro it has 6lb diameter and is nearly invisible under water. I was using 6lb mono and it was getting broke off too easy so I needed a little more strength but I truly think that smaller diameter line gets more bites. Just make sure you check the line often for freys on knicks. My only gripe with braid is when I get a knot in the line I can never get it out and I have to end up cutting the line at the knot and that gets expensive. I usually use 12lb mono for bass fishing on conventional gear.