Hello! It's great that you're planning to visit Skiáthos, Skópelos, and Alonissos. These islands are indeed breathtaking.

Best Time to Visit:
The best time to visit these Greek islands is during the late spring (May to June) when the weather is warm but not too hot, and again in early fall (September to October). Summer (July to August) can get quite busy and hot.

Route and Accessibility:
You can reach Skiáthos by flying from Athens, and this island has access to ferries and hydrofoils that connect to Skópelos and Alonissos. The islands are quite accessible by public bus circuits, taxis, or renting a vehicle for more freedom.

Accommodation and Booking:
There are plenty of guesthouses, hotels, and holiday homes available on these islands. Depending on your budget and preference, you can book your stay directly through hotel websites or through online travel agencies. Booking in advance is highly recommended during the peak season.

Clothing and Essentials:
Pack your summer clothes, a hat, sunscreen for sunny days, and also some light layers for cooler evenings. Also, as these are beach destinations, swimming suits, beach accessories, and a good insect repellant are essentials.

Health and Safety:
The general health and safety standards in these islands are good. However, always ensure you have travel insurance covering medical emergencies. Stay hydrated and use sun protection to prevent sunburn.

Local Etiquette and Respect:
Greeks are known for their hospitality. It's customary to greet with a smile and say 'Yasas'. Respect local traditions and places of worship. Casual but respectable attire is accepted in most places, but more modest clothing should be worn in religious sites.