The easiest way to come here is by airplane. Kota Kinabalu has an international airport with two terminals, one for regular flights and another for budget airlines.It is connected from most major cities around South East Asia and North East Asia. Brunei, Kuala Lumpur, Manila, Singapore, Hong Kong, Osaka, and Seoul are some major cities that have connecting flight to and from Kota Kinabalu.
Being on the Borneo Island, Kota Kinabalu is disconnected from the mainland Asia, and can be accessed by land only from within Borneo Island.There is a good road link from Brunei via Limbang, Lawas (Sarawak), Sindumin (Sabah), Sipitang town, Beufort, Papar and toward Kota Kinabalu. This Journey will take about 6 to 8 hours.
KK is a port city and does receive Ocean liners. I am not sure if any known Ocean liners make a stop here. There are ferry services from Labuan to KK, and vise versa, daily. This journey will take 3 hours.From Brunei you need to take a ferry to Labuan first (about 1.5 hours)before proceeding to KK by another ferry.

There are also ferry services from Nunukan, Kalimantan, Indonesia to Tawau.

KK city is only about 2km from one end to the other, and if you are up to it, you can easily walk from one place to another inside the side.

But many areas are outside the main city and need some kind of transport.There are three main modes of transport. Bus, Taxi and rented car.
The major bus companies that service routes in and around Kota Kinabalu are located just opposite the Court House, along Jalan Pantai (Beach Road), right in the middle of the city. Most buses operate with a 30 minutes interval.
City Bus operates two major routes one north of KK City and the other one toward the south of KK City. City Bus buses are all fully air-cond. Bus fare starts from RM 1 to RM 2.

1) Kota Kinabalu > Likas Bay Highway > Yayasan Sabah Building >King Fisher Park> Federal Administration Building > University Malaysia Sabah (UMS) > 1Borneo Hypermall > Alamesra Shoplots > King Fishers Park IV > University Apartment > Taman Indah Permai >Institute Technology Malaysia

2) Kota Kinabalu > Komplex Karamunsing > Sacred Heart Cathedral > State Mosque > Tanjung Aru Town > Terminal 2 (KKIA) > Tanjung Aru Beach
PUT operates on two major routes, and most of the buses don’t have air conditional. Bus fare start from RM 0.60 to RM 2.00.

1) Kota Kinabalu > Karamunsing Komplex > Luyang Phase 1, 2 and 3 > Damai Commercial Centre > Foh Sang > Taman Fu Yen > Taman Jindo > Lintas Plaza > Bukit Padang > Taman Khimat > Beverly Hill Apartment

2) Kota Kinabalu > Karamunsing Komplex > Sacred Heart Cathedral > Sabah Museum > Queen Elizaberh Hospital > Taman Fortuna > Lido Market > Towering Commercial Centre >Penampang New Town Shoplots> Kadazandusun Cultural Association > Donggongon Town
Tut has non air conditional buses, and bus fare from RM 0.60 to RM 2.00

1) Kota Kinabalu > Komplex Karamunsing > Sunny Garden > Kian Kok Secondary School > Likas Sport Complex (Outside) > Shan Tao Secondary School > All Saint Secondary School > Kampung Likas > Kolombong Industrial Area > Northern Bus Terminal > Inanam Township
The mini-bus station is situated next to Wawasan Plaza at the southern end of Jalan Tun Fuad Stephen. Mini-bus mostly goes to areas where the Major bus companies do not go. Noted: Most mini-bus has very little legs room and almost all does not have air condition. Mini-bus can also be very untimely, it will only go when the bus is full. Fares are between RM 1 to RM 2.

Some notable places cover by the mini-bus are Papar, Lok Kawi, Kinarut, Telipok, Tuaran,.

These fares could have changed since publication.

1Borneo provides free shuttle bus service  to and from 1Borneo. The timing of the bus service is given below. You will have to book your seats at their counter at least half an hour in advance.