I too had read that Unofficial guide, among others, and was totally paranoid about calling in for my ADRs, specifically for CRT! I took the advice to heart, because I didn't really know any better! I set my alarm clock and was wide awake at 6:45. I waited with the phone and credit card in hand and as soon as the clock said 6:59, I started dialing. I got through pretty quickly, only on hold for a minute at most and then made my ADRs. I started with CRT and requested for a late breakfast time on day 182 since we're staying on site. She gave me 10:15. I have BBB at 8:30 that morning too.
It wasn't all that hard! I have to laugh at myself now for being so stressed about it all worrying that I wouldn't be able to get my ADR. If you want to guarantee a time, just make sure to call at 180. I honestly don't think you even need to call right at 7AM.