1) There is no general timeline. Everyone has their own set of circumstances which will significantly alter any given "timeline." One person may not have any work/school and thus has all day everyday to study while someone else may still be in school, working part-time, have kids, etc. You will have to figure out what works best for you given your free time, study tendencies, financial circumstances, etc.
2) That said, you want to have enough time to properly prepare yet not too much where you will burn out. This, again, will be very different for each person. Maybe you are already scoring in the 165+ range and will get into the 175+ range within 3 months of prep (amazing!!!). Maybe you are scoring in the 140 range and need 6 months to get into the 155+ range. Find out what you goal is, where you are, and then figure out how to get there given #1.
3) Do not plan on re-taking the test. This is something you should only take once. Yes, there are plenty of times where re-taking the test may be the best idea, however, this should be a last resort decision AFTER you take the LSAT. You shouldn't schedule it in. That said, I understand your concern that, in the event of you needing to, you would like some wiggle room to study and then retake. This is fine to some extent, but leads to #4.
4) When do you know you are ready? This is partially going to be a feeling - you will know when all the extra studying in the world is not going to do anything for you. At the same time, you should be keeping track of your progress on PTs. If you studied correctly (PROPER un timed practice > PROPER timed practice > FULL test conditions), by the end of your prep, you should have a very strong idea of your average band. When that avg. band isn't consistently improving by more than 3 points, you are pretty much done.
5) When should you retake? Only if something horribly wrong occurs. If in the middle of your test you get a giant pain in your stomach that screws section 4 and 5 over for you. If all your pencils broke during section 2. Or, maybe you realize after the fact that you really didn't study correctly. That during your "full test conditions," you gave yourself an extra min. to bubble in, you gave yourself an extra 10 min break to go out and get coffee, etc. If you can identify specific and significant factors that heavily and negatively affected your score, then you can consider retaking the test. Other than this, however, it will be a complete waste of your time. Remember that any given score is statistically the same within +/- 3 points or so. And after 165, you are statistically more likely to score lower on a re-take than higher.
6) So what does all of this actually mean in real terms for you? It sounds like you are a freshman or sophomore in college. It also sounds like you want to go straight from graduation to law school (i.e. no grad school/work). I would strongly encourage you not to focus too much on the lsat until the end of your junior year. Between now and then, I would take a few sections just to see where you naturally are. I would also do all your studying on the test between now and then on any free time. This means setting up a study schedule for the end of your junior year. I would also slowly go through a study book on your free time (kaplan/powerscore). Again, only on your free time - instead of watching TV kinda thing. This way, by the time you hit the ground with your LSAT studying, you will be ready.
7) I would allocate between 3-6 months of prep prior to the October test. This way, you will have all the summer to hit the LSAT hard and will avoid running into finals/midterms during your prep. I would personally start sometime in april/may and pick it up big time during june or so. This way, if you did need a retake, you have dec. waiting for you, or even feb. if a school accepts it (they usually don't).
There are plenty of resources on this and other sites sa to how to properly study. At first you want to focus on un timed practice. This is not leisurely practice, rather you need to go through each answer choice, write down why each one is incorrect/correct, and double check it before you move on. Once you are scoring in the 175+ range un timed, you can move on to timed section(s) practice and then to full test conditions.