The thing to keep in mind is that this plugin is SUBTLE. Most of the differences between analog tape and digital recording are not as NIGHT AND DAY as the pundits would like you to think (not anymore since digital has improved).
Put it this way: if you put AC1 and AC2 onto your mix buss (and only that) you will not go WOW THAT'S SUPER AMAZING! Chances are you'll be like the intern we have that did that and went: "wow, I don't hear much difference at all...." Of course, if you pull up a vintage tape formulation and slam it to tape compression hell you can't miss the changes--but the changes are usually for the worst.
After spending a lot of time with this plugin--I've used it on almost every channel of every mix I've done for the last few years--I have came up with a number of observations about using Analog Channel:
1.) Setup your channels like you would in an analog setting. AC1 (the console) before the tape (AC2) on all channels. Depending on how you envision your session you can place AC1 first, the rest of your pluggos, and then AC2 (emulates a more 'mix it as we record' vintage/British style of recording), *OR* run AC1 into AC2 (to simulate a more modern approach).
2.) As a general rule AC2 should be set identically from channel to channel across the mix. This adds that sense of homogenity to the mix a tape machine will offer.
3.) Be extremely careful with the bass boosting "head bump" function on your channels. I generally run this at 0% because it can build up badly once you've summed together 24+ tracks. If I'm looking for that expanded low end response from AC I will save that for the master buss. In general a 25-50% head bump is about all you need.
4.) Don't drive into AC1 or AC2 too hard as it will compress and distort like the real hardware. There is a reason that over saturating tape or really slamming the console was rarely, yet deliberately, done. Choose your settings wisely! Don't go overboard.
5.) A lot of times it is most effective to mix with AC *OUT* of the mix. That way you maximize your mix before adding that extra depth and fatness.
6.) I find it best to simulate one type of analog machine that material was tracked to, and a different model that is being mixed down to. My standard choices are track to the Studer model, and mixdown to the Otari or Sony model.
7.) Be careful when messing with under or over biasing. Choose this deliberately for an effect, or to recreate the sound of a particular engineer, album or studio.
8.) Best of all is to have fun. Analog Channel is one of the more fun plugins out there because of how creative you can get with it.