Every January since 2012 -- as part of my Hong Kong/Singapore Startup Strategy Offshore Elective at Babson College -- I leave my house and arrive 27 hours later at a hotel in Hong Kong. 11 days later I leave a hotel in Singapore and arrive back where I started about 27 hours later.

I am sure there are longer flights but this one -- but when you add in the visits with startups, accelerators, professors of entrepreneurship, and investors, the physical challenges of remaining alert throughout each day are considerable.

If you find yourself regularly taking such long flights -- or are about to embark on one for the first time, there are six things you might consider doing that help me keep going.

1. Drink water, not alcohol

Alcohol is often available on long flights. But I tend not to sleep very well if I consume it. So I tend to stick with water and try to drink lots of it during the flight.

I also tend to minimize alcohol consumption once I arrive in the countries I visit. In general, I am always trying to avoid consuming things that might make it harder for me to sleep.

That means I sometimes skip dinner -- especially if I am planning to sleep as soon as I return to the hotel.

2. Get an aisle seat

I like to get up and walk around during the flight. If I have a window seat, it will be difficult for me to do that -- especially if the people in the middle and aisle seats are fast asleep.

Some people can sit in the window seat and sleep for 16 hours straight. If you can do that, I would recommend doing that.

3. Pack light

The most controversial thing I do on these trips is to pack everything I need in a carry on suitcase. This means that students always look at my bag incredulously and ask me if that is all I have.

But I am happy to explain to them that because I pack light, my luggage does not get lost in transit and I won't hold up other people because my suitcase does not arrive on the conveyor belt for 45 minutes.

I plan to do laundry during the visit and have enough clean clothes for the entire trip.

I have no proof of this -- but I think packing light reduces my stress level.

5. Avoid late night activities

If you are on a business trip, you may find it impossible to avoid going out late with potential customers.

During these long trips, I hardly ever need to stay out past 10 pm. If I have a choice, I will try to get to sleep before then.

Obviously some people can stay out until four in the morning and wake up three hours later and make it through the day.

I am long past the age when I could do anything close to that.

And I have noticed that my students who do that tend to fall asleep in meetings and get sick -- sometimes requiring a visit to a health clinic towards the end of the course.

I usually enjoy one or two later evenings during these trips but I am always trying to make sure I can get enough sleep so I don't get sick.

6. Consume caffeine

The one drug I consume consistently on these trips is caffeine. I drink coffee in the mornings and tend to keep doing so until lunch time -- at which point I cut off consumption so I will be able to sleep during the evening.

If you are making the investment in a long business trip, it is essential that you maintain a clear focus on why you are there.

For most people, the goal is to build relationships that will generate business for your company.

That means you should get enough sleep, stay alert, think clearly, and strive to stay healthy the entire time.

These six tips work for me -- your mileage may vary.