How to get 90%+ TT?

What MA owes you is part of it. The balance of what is available to be mined affects it. So tell those crafters to keep pushing it through the machines.

Some areas just don't have resources, there have been areas that I have checked several times over the years and nothing is there. And there are areas that nearly always have deposits. Premined..... well it might affect it if the other miner has your same skill and same tools. Otherwise I don't really think so. I was mining on Bakunawa, a miner crossed my path, I just watched him run along dropping probes... So as a caution I changed directions. Was having an OK hit rate, and came across claims, but I was still hitting. Seen that miner cross back through my radar the direction I was going. I said the hell with it and followed him using my mining secrets. I was hitting the same ores and En he already had claims on, near his claims. I am guessing I was probably running at a different depth. But I continued and even popped a 71 ped lyst near were he was not 5 minutes before. No amp, total probe drop 250 PED, TT of ore and en was 300+. Premined I dont think is too much of a factor.
Deposit are all over, your skill and tool comb determines what you can find. Deposit are a different type of mob in my mind. The probe is your ammo, finder is your gun. If you point your gun at nothing and fire it, you will NOT get any skill gain. But if you aim at a mob and fire, you may get a skill gain, and you can only get a gain while aiming at something. Mining is like hunting in the dark with a shotgun. If you get a skill gain, there is something around. Learn what the gains are telling you. Also REMEMBER just because you get a gain, DOES NOT mean you will find the deposit. You may not have the skill or tool to reach the depth. It might be shallower than your tool, I have switched to lower finder to find deposits. Also note the there can be more than one claim in the detection radius, not like years past, I once had 9 claims from one spot. I got the pic to prove it somewhere....
My history.... I have been playing since 2001, Mostly mining. Played regularly until sometime after the big mining changes. Had some life changes and would only log in from time to time. Until the last year I have been on fairly regularly. Been finding the mining system wasnt as wrecked as I thought before, and seems to be working like before. Maybe after the revamp it just need time to rebalance. For 1 year before the mining revamp I did not have to deposit. Here in this last year I think I purchased a few AMDs and Box keys. To date have not with drawn any deed revenue. No actual deposit per say. I have earned some PED from PEDFLOW.com. I survive on 2-300 PED weekly turn over, with out deposit.
I very rarely use amps, and if I do, I crafted it. I can only make LVL 1 and 2. To me you do not need amps to turn a profit, they are mostly for that HOF glory.
Also another thought, ever noticed that mobs typically travel in certain directions? LOL that will make them think....

Oh forgot to mention FOMA. It is not inside mining. You're outside on an very large asteroid in space. That has Bio-domes setup so you do not need a space suit to survive. BTW space suits would have been cool. The composition of the asteroid surface is a higher density than that of the planets causing the finder ranges to be reduced. At the same time that it reduces the range it compacts the deposit together creating larger but fewer finds. Other than that it's the same mining system. Between the last 6 runs of 120-160 PED I'm sitting even. I've hit 4 globals 2 no amp 2 with lvl 2 light.
I'm currently using F-106 with 1 and 2 depth enhancer. It's ready for T3 but the 300+ TT mats are nearly 800+ with mark up. Welcome to the life of a a budget miner, where you make every probe count.