Certainly, I'm glad you're planning to visit the interesting towns of Tawau, Semporna, and Sandakan in Malaysia. Here are some travel tips to make the most of your trip:

Best Time to Visit:
The best time to visit these places is generally during the dry seasons, which run from March to October. However, as weather can be unpredictable, it's best to check the forecast before travelling.

Route and Accessibility:
These towns are all in the state of Sabah, on the island of Borneo. You can easily get your connective flights/book busses from the capital city, Kuala Lumpur, to these towns.

Altitude and Acclimatization:
These cities are not high-altitude destinations, but do take time to adjust if you're travelling from a significantly different climate. Also, keep hydrated at all times because it does get quite humid.

Accommodation and Booking:
There's a good variety of accommodations in the mentioned towns, ranging from budget hostels to luxury resorts. It's wise to book early if you're travelling during peak seasons.

Clothing and Essentials:
You will need light, breathable and comfortable attire considering the tropical climate. If you are planning for diving, hiking, or a visit to the rainforest, prepare suitable equipment or clothing. Don't forget to bring a good sunscreen and an insect repellent.

Health and Safety:
Stay hydrated and eat well-cooked food. If participating in adventure activities like scuba diving, follow the guidelines provided by the local authorities.

Local Etiquette and Respect:
Malaysia is a multicultural country, respect local norms and traditions. Dress modestly during visits to religious and rural places. English is widely spoken but learning few local phrases can help connect with locals.