Let me share some thoughts as well. I've got 30+ toons leveled 1-80, more than 10 85s as well (0 suspensions for botting, 0 permabans), so you can trust my experience.
1. Do NOT use bot for leveling 1-60. Make 1-2-3 additional RAF acc(s), hit level 10 by grinding in group (it takes me ~1 hour to make 4 lvl 10s just grinding mobs with one character, others were in group on /follow). Then take one lvl 80-85 and boost them through Classic/TBC instances. If you don't have a high level on a server you're planning to bot on, then just buy some gold (2-3K is pretty enough on Russian realms, but I would recommend to take 4-5K for Eu/US players) and spam for payed boosters in any major city.
It takes me 12-15 hours to get 2-4 lvl 60 toons this way, so I consider it is the fastest one so far (and 100% safe lol). One more point I would like to draw your attention to, is that in Cata many Azeroth locations have been redesigned and now old 1-60 profiles are broken while new ones are still much less tested (=more stucks, more danger situations).
2. Use only grinding/farming profiles. Questing sounds cool, but it's still very unrealiable. Both IB and PvP bot are rather noticeable for experienced players. Also, questing profiles forces your char to dart here and there in places where most players do leveling while most of grinding profiles are far from it. Less players seeing you = less potential whisperers/inviters/reporters you get.
3. Gear up your bot as cool as you can. People expect bots being poor/out-of-spec/wierd geared. Pimp your char like a fancy twink and noone will ever suspect it of being botting. I swear. Even if your character keeps grinding silently, people still think that it's just a too proud guy who doesn't want to deal with n00bs. Also, good gear greatly decreases the time you have to spend in one location, which is another safety factor.
4. Level up skinning ( and dig for grinding profiles in beast-populated locations). A continuous grinding looks much, much more reasonable if you kill mostly animals and skin them. People will just think that you are leveling skinning/farming leather. Also, skinning brings enough money to keep a char fully pimped while leveling (watch the point #3).
5. Monitor game chat. Personally, I attach Pirox in monitoring mode to my HBs, it has nice chatbot built-in and a set of sound signals for most in-game events (chat and queues).
6. Don't trade large amounts of gold. Better trade mats instead. This rule will keep you away from bans for goldselling.
7. Always have a legend. Always think what to answer to a whisperer about your wierd gamestyle. Skinning and good gear are your friends here, as well as old profiles (for example, almost noone do quests in Blade Edge's Mountains / Shadowmoon Valley, so for me it's a safer choice comparing to, say, Nagrand. Even though BEM/SV aren't best places for skinning). Also, you better have a legend about how did you get all that gold/achievements or what you're botting for.
Hope you find it helpful, otherwise I'm sorry for spending your time reading this. It's not only about the safest way to bot, but I believe my tips will help you make your botting experience a bit safer.
P.S: I have skipped some obvious things like "do relog periodically", "do not bot 24/7" and so on, you can dig 'em in dozens of similar guides and topics here, just use the search.
Best regards,
nforcer.