I'm also a casual botter. Since WoW has come out, I've had two kids and now have less time to play WoW. Botting has made it still possible to play and be a parent.
Most bots are nailed by player reports. If your AFK botting around the timeless isle during prime time your more likely to get reported than if your leveling up an alt. If your going to bot rep, make sure you are close and can respond if someone sends you a group invite and a tell. I use the addon WIM to make sure no tells get lost in spam chat. I just respond telling them "No thanks for the group, wife will be home any minute and noone needs wife aggro". That usually gets a laugh and they leave the bot alone after that.
Any AFK botting is more dangerous. I've walked back into my office and seen my bot stuck on a wall, or running around in a pattern. If a character is running 20 years back an forth in a line for 30 minutes, it will look very suspicious to anyone.
Another thing that will draw suspicion is if you unload lots of ore/herbs on the auction house. I've used gatherbuddy many times with no problem to level up blacksmithing, engineering, jewelcrafting and alchemy on alts. That's hours of farming. Instead of pushing all those mats onto the AH, they were burned leveling up alts profs. This makes the chances of being reported very small.
To earn gold I've been running the dailies. I've not make a ton of gold off them, but I've not been hurting. I've had enough gold to get epic flying on all my 90s (8) and buy mats from the AH when needed.
In summary think about it like this -- if you were not botting, what would piss you off and make you report someone.
1) Someone grinding away on mobs that your doing manually.
2) Someone putting up mats on the AH for less than you can.
3) Someone causing your BG group to lose because bots don't have strategy in BGs
4) Someone taking your mobs/nodes when your trying to play the game.
5) Someone not responding to tells/group invites.
Limit those situations where this would happen and your less likely to be banned.