Hi Sayhello,
Unfortunately, I didn't do a trip report for Greece because there were a couple of people who already had. However, I did add comments to the end of one of them about some things that hadn't been addressed.
You will LOVE Greece!!! If you go during the summer, it will be very hot. Take a hat, wear it, and take breathable clothes that can be easily washed out in the sink. Our ferry crossing from Santorini to Crete was very rough. It seems as if it is hit or miss with this, but make sure you take something for motion sickness if you are prone to it. I flew into Athens a day early and stayed a day later to see some of the sights
ABD wasn't going to. The day I landed I saw: Syntagma Square, Changing of the Guard at the Parliament Building, National Gardens(a disappointment and didn't feel too safe walking it by myself in the day--concierge said definitely don't do it at night!), and Bernaki Museum. The next day before the welcome dinner started, I did: Hadrian's Arch, Temple of Olympian Zeus, New Acropolis Museum, and the Plaka(shopping area at the foot of Acropolis). On the day ABD did the Acropolis, I used that ticket to see the Agora(at the foot of the Acropolis) and then went to get authentic Greek sandals from the Poet Sandalmaker(look at reviews on tripadvisor) in Monstrivikos(sp?) Square--you exit the Agora in this square. I then got something to eat and caught the hotel shuttle from Syntagma Square back to the hotel. On the day the tour ended, I flew back to Athens and stayed at our previous hotel for one night. I used the day to see the National Archaeological Museum(take the metro from Syntagma Square--it's about a 4 block walk from there).
Make sure you take advantage of the Intercontinental Athenaeum hotel shuttle. It takes you to Syntagma Square where there are lots of eateries(McDonald's--I know, but sometime you just want something familiar, Hard Rock(a couple of blocks away), and other Greek style eateries. I believe there is even a Starbucks nearby. The main touristy shopping district(american stores) is also behind the McDonald's. The Plaka is where you go for the Greek items. Be sure to comparison shop before you buy. You can go around the corner and that shop is selling the same item for more or for less than the shop you just visited. I hope this helps.