I just started rebuilding, but have been using 2 Pro Tank IIs everyday for the last 4 mos. In search of the perfect vapor, here are my opinions from my trials and errors (and heavy research on Ecig Forum and the internet)
1) Get an air flow controller. Makes a huge difference. I think they are around $5. Absolutely get one. I think it makes a better contact too with the coil and battery
2) I finally started studying the bottom of the coil where the silicone grommet is located. I have had bad batches (started getting burning taste way too soon - a day later after putting a fresh coil in) and noticed on those bad coils the grommet was squished. I pulled the bottom pin out a tiny bit, let the silicone grommet expand, and it worked much better, but ultimately it will get squished again and go bad. You can read on the internet about the bad batches.
3) Buy the 5 packs of coils on line. My local shop charged $20 for a 5 pack. You can buy a 5 pack for about $5 online. So cheap that you can just toss them when you get a bad one.
4) I have found that brand new, obviously, the coil works good. But then it goes bad a day or two later. By that I mean, the flavor is muted and much drier. For me, a quick rinse and dry burn (doesn't take much, the silica wick has hardly any juice burnt) did wonders and helped make that coil last about a week. So See no. 3. Every week, I toss the old one and put a new one in. Lately I have been putting two strands of silica wick on top of the coil for the flavor wick. Or organic cotton. You can reuse the flavor wick, but rinse it out good. Problem is that it's small and I have lost more than a few down the drain.
5) I HATE leaks and gurgling and shots of juice in my mouth. A lot of the time you can turn the airflow controller all the way open and turn up your watts and burn off the excess. Sometimes, just taking the coil off and blowing it clean works too. If it still leaks, see no. 3. Toss it and put a new one in.
6) I moved up from 1.8 coils to 2.5. Then down to 2.2. I think 2.2 is a happy medium; maybe even 2.0, but I haven't tested enough to know. My understanding is the lower the ohm the less power it takes to heat it. So that helps on lower powered devices (I think)
7) the base DOES wobble and doesn't always fit correctly. Eh, I don't find it to make much issue. From a youtube video, I learned to listen for a click when screwing the coil in. It should be snug. (But not too snug, then you run the risk of squeezing the grommet) I can tell when the chimney isn't on correctly or when the coil isn't in the base correctly because the the coil base won't screw nice and easy to the Pyrex tank. When it screws in nice and easy, you will have a good vacuum. If it feels "clunky" when it screw in, you probably won't have a good vacuum and it will cause a leak. Sometimes, all it takes is to rescrew in the coil.
8) Finally (I have done a lot of testing and read a lot of posts on Ecig forum), in my opinion, sometimes too much wick is not good either. It seems counter intuitive, you want a lot of wick around the coil because it plugs the hole between the fluid and the hole under the rubber grommet on the chimney. And it should, in theory stop the leaks.....But too much wick means not enough liquid gets through and then you get dry hits with vapor that lacks flavor. It's about finding the happy balance.
8.5) When installing a new coil, I fluff the silica wick to make sure it covers the hole before screwing it in. May help sometimes.
8.75) Oh, in my opinion, you want to let the vapor come to you. If you suck too hard, you tend to flood the wick and depending upon your device, you may not have enough power to burn it off. So steady pulls let the vapor come to you in line with the heat of the coils.