In order to keep an excel sheet up to date real time, while we both accumulated information we decided to create a Google Excel Doc where we could both edit it instantaneously. Here is a screen shot of how we organized our budget, our timeline, to do list, places we wanted to see, ect. I highly recommend using this platform to organize yourself a bit :)Then we started filling it in! I used sites like Nomadic Matt, the savvy backpacker to get averages on how much it would cost for hostels, food, transportation, activities, etc.
And we created a general timeline for ourselves, we don't want to plan everything out to a "T" but we do want to at least have a general idea, and make sure we end up in Athens at the end of the trip to catch our flight!
My sister and I are the adventurous type, so we have been looking for activities like parasailing, scuba diving, and more, in these cool locations, and I have found that Nomadic Matt's travel guides are a really good place to start! I have been looking through the Greek Isles Activities on his site, and then taking it a step further to research the individual companies that we might make a reservation through and also so I can see how much it will cost.
So far this is been the method to our madness I hope it helps you get started in planning your next trip!
With Love, G