Is it rude to decline alcohol at a business dinner?

It is acceptable to decline politely. If you do not drink, it is common to just keep your glass full or hold a small amount to participate in the 'cheers' ritual.

Should I tip my taxi driver?

No. Tipping is not part of Korean culture and can even be seen as confusing or patronizing.

Planning a Productive Business Trip to Seoul

Focus your itinerary on a single district to avoid Seoul's heavy traffic, and use the AREX train for airport transfers to guarantee arrival times. Book your meetings for mid-week, Tuesday through Thursday, to ensure maximum availability from local counterparts.

Select your district based on industry. Stay in Gangnam if you are in tech or finance, and Gwanghwamun or Yeouido if you are working with government entities or media conglomerates.
Secure a T-Money card immediately. Upon arrival at Incheon, buy a T-Money card at any convenience store. Load it with 30,000 KRW; it works for all subways, buses, and even taxi payments.
Use Naver Map or KakaoMap. Google Maps does not provide walking or transit directions in Seoul. Download Naver Map and switch it to English to navigate meeting locations accurately.
Arrange local connectivity. Pick up a portable Wi-Fi egg or an eSIM at the airport. Public Wi-Fi is everywhere, but constant connectivity is vital for Kakaotalk, which is the primary business communication tool in Korea.

Is it rude to decline alcohol at a business dinner?: It is acceptable to decline politely. If you do not drink, it is common to just keep your glass full or hold a small amount to participate in the 'cheers' ritual.
Should I tip my taxi driver?: No. Tipping is not part of Korean culture and can even be seen as confusing or patronizing.