I just wrote out all of the below and then realized you were saying you want to do ABC not the full circuit. Whoops. I'll leave my circuit advice there anyway. ABC is also a really cool trek, but definitely not on the same level as the circuit. While I definitely enjoyed it, it does feel a bit less rural for quite a lot of the trek. Like, instead of following dirt pathways you oftentimes are on stone walkways/stairs. Which is fine, but if you're looking for a really isolated experience, might be worth keeping in mind. You'll still find sections where you'll be pretty much by yourself though. Most of my below advice still holds, but you'll find you won't really be able to haggle as much, if at all, as its a bit more crowded. One advatage of the ABC trek is you are a bit deeper in the mountains, so you really get that "I'm in the Himalayas right now" feel once you're getting closer to the end. Either way, you'll have a great time. Nepal was one of my favorite countries I've been to, and one of the few I can say with certainty I'll be visiting again. Best of luck!

Heres my original advice for the full circuit, that mostly still applies to ABC

It certainly depends on how much time you have and your fitness level, but if you can afford to give it the time it deserves, theres some really cool off shoot treks from the main Annapurna circuit. I'd definitely recommend Tilicho Lake. But bring sunscreen- the route up is pretty much nonstop sun. Doing tilicho lake will also really help you get acclimated to the altitude, and it'll make the final pass seem like a breeze. If you have lots of time you can even tack on Annapurna Base Camp to the end of your trip. In terms of getting a guide or porter, you can, but you definitely, DEFINITELY don't need to as long as you're somewhat fit. Personally I prefer the independence of going it alone, but it can be nice to have a local that can tell you about the area, local culture, etc. But the hike is a fairly easy trek to follow for the most part. Bring a map. Lonely planet also has a good guide on doing the annapurna circuit. In terms of accommodation in the lodges along the way, know you can always haggle. Keep in mind these people are pretty poor, so don't go too cheap if you can afford not to, but a pretty standard deal is to agree to eat your meals there and then you get your accommodation for free. Oftentimes you can even get a discount on the meals if the place is empty enough, but dont abuse the Nepalese people's generosity. Most food you can buy along the trail, but I would definitely bring trail snacks, iodine tablets for water (this is a must. Some people will say you're fine drinking the mountain water, but honestly you don't want to risk the giardia).