Wow... it's been long enough, eh? If you have read Parts one & two you should already have a good idea of the sort of trip you have in mind. Ideally you have a notebook or binder where you are keeping track of these sorts of things- lists of options on where you want to sleep, rough ideas of your budget, and the sort of traveling you intend to do. Now you need to decide where you are going and how you are going to get there.
Ideally you would have covered this when reading Choose Your Own Adventure Part 1 but I cannot safely assume that you have all read that, so we will do a recap. Ya need to know where you want to go before you can go, ya know? Basically what you need to do is open a fresh page in that adventure book you have set aside and start jotting down all the places you want to see. At this point, don't be worrying about your time frame, budget, etc....simply unload all of your dreams of exploration. Machu Picchu? Eiffel Tower? Great Wall of China? Rome? Bristol? Timbuktu? Isle of Man? Bruges? Maine? If you wanna go there, write it down! Don't think this only takes a minute or two- it takes a lifetime. This is a page you will hopefully be adding to and crossing off of for many, many years to come.
Once you have a good sized list, theeeeen you can be realistic. If you want, you can go all crazy and sort the places by continent or general area (you can even color code it if you want to). What sites/cities/towns can you group into one trip? Once you have grouped them, play the priority game and choose the trip you'd like to take first. Make sure to keep in mind how much time you'd like to spend in each area - an hour? a day? 3 days? two weeks? Completely up to you! This plan is a draft...the reality of this list being your final plan is slim, but it is a very important step.