Meteora probably doesn't need a lot of additional information. The conglomerate rock formations inspired climbers for ages and there are 2 major guidebooks. Although you might find shorter routes in the shade in summer, wanting to climb long multi pitches requires to get up early and make sure you know the access as the millions of paths between the rock towers can be hard to navigate.
Bolting can be very tough on your nerves with often just one or two bolts for lengths of 40 meters. Make sure you start with grades way below your limit to get used to the strange rock and bolting!
Pili (parking at N 39°27.618' E 21°36.095' at the old bridge; cross the river from there and follow the path (and the water pipes) left and then up for about 20 minutes) is the sport climbing spot in Greece, especially in summer. With about 65 routes in grades starting at about 6a it offers a lot in perfect limestone. Climbers built a flat platform at the base of the cliff to relax and chill during the heat of midday. Drinking water is available from one of the pipes. Wifi can be found at the coffee next to the bridge.
Up to date topos can be found at Climbgreece.