Is it better to book local excursions / tours in advance or book once your there? What about transportation?
Please forgive me for not knowing how ask these questions properly.
I can learn reasonably fast, however, with a bit if guidance.
Probably.

Welcome to Fodors. We moved your thread to the Europe Forum and tagged it for Greece.

Strange -- I would have sworn I responded to this post!

You don't need to take any tours unless you want to -- these places are easy to visit on your own.

It sounds like you would benefit from a good guidebook or two. IMO, the Rough Guide is quite good for Crete and other parts of Greece.

If you haven't already seen it, you might find some useful information in my trip report. The section on Crete (including both Chania and Rethymno) begins with post # 48.
With Gratitude for a Glorious Solo Month in Greece

Loved my visit to Crete. Lonely planet used to have an excellent guide book to Crete but I have not looked at the recent ones. It is a big island. Really need a car in my opinion.
If no car probably tours are your next best bet.

I liked the OLD Lonely Planet. I'm not a fan of its new format.

The public transportation system in Crete covers most (all?) of the highlights.

Loved Crete and Paros!

I went to Crete in October 2025. Unfortunately I only gave myself 2 night and most of 3 days on Crete. I spent a night in Heraklion and a night in Chania. I perceived Heraklion to be a decent enough city to visit even though it is under-rated or disregarded on travel discussion threads. Yeah I know my taxi from the boat to the hotel passed a street with dumpsters that smelled like garbage, I saw a retaining wall instead of a beach, and its a slightly big city compare to other places on Crete. In Heraklion I had time for the ruins of the Minoan site of Knossos; and the archaeology museum in Heraklion, in one day, and the next day the restored Venetian fortress Koules that I paid to go into briefly. The city was badly destroyed in the battle of Crete in World War II. There is the reconstruction of the old town hall and maybe other monuments.

Chania is ok too but its a smaller town and most of the tourists seemed to be gathered at some restaurants with outdoor seating next to a little bay right by another Venetian castle. There was a good maritime museum with two branches about 300 yards apart.

I would have added Rethymno if I had added in a 3rd town. There is the Samaria gorge. Check the Rough Guide to Crete. I'm not sure if the Fodors guide has a good section on Crete. There is also the Lonely Planet guide to Crete.

Edit: I took a taxi to my first hotel, a bus to Knosos, a bus to Chania, and a bus to the boat back to mainland Greece. The taxis were just waiting by where the boat docked. The local and longer distance buses go to most places you probably would want to go. I have traveled to different parts of Europe 7 times. I have never rented a car outside the United States.

First of all you must know where you want to go in Crete and what you want to see.
Only then you can discuss about transportation or guides for some particular sites.