Hello! It's great to hear that you're planning a trip to South Korea. Visiting Seoul, Incheon, and Jeju will indeed be a fantastic experience. Here are some tips for your travel:

Best Time to Visit:
The best time to visit South Korea, including Seoul, Incheon, and Jeju, is during spring (April to June) or fall (September to November) when the weather is mild and the scenery is gorgeous.

Route and Accessibility:
You can easily access South Korea via multiple international flights landing in Incheon International Airport (near Seoul). From Seoul, you can utilize the KTX high-speed train to reach major cities or take local flights to islands such as Jeju.

Accommodation and Booking:
Seoul, Incheon, and Jeju offer a wide range of accommodations, from luxury hotels to budget-friendly guest houses. Booking sites like Booking.com, Agoda, or Airbnb can be utilized for reservation in advance, especially during peak seasons.

Clothing and Essentials:
Pack according to the season of your visit. Usually, light clothing is suitable for summer, while spring and fall require a light jacket. For the winter, make sure you have heavy coats and thermal inner wear. Essentials include travel adapter, toiletries, comfortable shoes, and sun protection.

Health and Safety:
South Korea has well-developed healthcare facilities, but travel health insurance is advised. Follow standard safety precautions and stay updated with travel advisories.

Local Etiquette and Respect:
Koreans value politeness and respect for elders. When greeting, a slight bow or a handshake is customary. One should not call someone older by their first name unless invited, and it’s polite to accept things with both hands, especially from someone older.