How to avoid luggage being lost in transfer?

Never put anything in your luggage you can not live without, if you need to take something that is very important for you, keep it in your carry on.

As the other answers state, make sure you have enough time between flights but not too much. One to five hours are the numbers I have seen reported on this site more than once. If your layover is long, say 8 hours or more, your best bet may be to not check it through.

The rest of this answer is more how to lower the impact of luggage that does not make the same flight you do. And on how to get it returned to you when it does miss the flight.

Have one set of clean clothes (from the skin out) in your hand luggage or at least clean underwear, so that if your luggage is late, you can clean up with your own clothes.
When luggage goes missing, mostly it is just delayed and may follow you to your final destination the next day or, (depending on the airline and airport) can be collected the next day. Having some clothes makes you will not be caught out.

Make sure you have your contact details on and in the case, so that you can be contacted when they find the case without the flight labels. If you can be reached by phone while on holiday, put your phone number (in international format, so with the + and your country code) as the top line. For the address, either put in your temporary address on the way out and your home address on the way home.
Or, if you have someone near home who will be home while your house is empty, their address and phone number.
There are many different kinds of suitcase labels available, (and you can even make your own if you can not find anything.)
And put the information inside your case.

And be sure to report your luggage missing, with the address and telephone number you can be reached.
Ask the staff of the lost luggage office what to do and what you get for not having your luggage right there. Some people report having been given nice amount of money to buy emergency supplies. (Others have reported not getting anything, so you will have to wait and see.)

Nothing really. The probability baggage missing a connection diminishes very slightly though if you:

1. Do not have tight connections. Anything less than 45 mins is tight but it many modern airports the probability is higher that you miss the connection than your luggage.
2. You fly the different legs on the same airline. In some airports this makes no difference but using different airlines can be more risky especially with tight connections.

Nowadays I find that missed connection means the baggage is much more often delayed than lost, so if you stay at your arrival city at least one day before heading on a tour or transport to another city, the chances are that your luggage will be with you shortly. Remember to have all essential items with you in your carry on, not just in case your luggage gets delayed but also so that you have access to items you need in case your flight takes an additional stop due to technical reasons, weather or even if your connecting flight is delayed until the next day.

My tip is to not worry too much, and to be careful to avoid valuables in the checked baggage (as the airlines officially recommend).

As opposed to the OP, I rarely travel with less than two connections. Over the last 15 years, I have traveled more than 50 long haul trips with multiple connections, often over multiple airlines, sometimes from multiple alliances in the same trip; some 20 airlines in total. In some family trips, I even checked 15 bags over two connections. My tally, over these hundreds of flights and hundreds of bag checked is as follows:

• One time, I was told during my third flight by the airline that some bags would not make it. They were delivered the next day, as promised.

• Two times one of many bags was not present, and in both cases it was delivered to me the next day; one of these cases, the bag had lost a handle and with it its tag. Without the tag and with the description "black bag without handles" the bag was delivered to me.

• One time a playpen was lost and never delivered. In retrospect, the tag was put on a very weak handle, so it likely fell off. My credit card insurance happily paid for the lost item, after a crappy airline declined to pay for it.

The other hundreds of times, my bags made it without issue.

Are there any tips how to minimize this from happening?

Unless you're asking this as a member of the Operations team of an airline, there's not much you can do to minimize the risk of lost luggage. That being said, statistics are generally in your favour:

From the data available here which is sourced from Air Travel Consumer Report issued by the U.S. Department of Transportation, 0.021% of luggage is never found

So you'd have to fly 3300 times before you'd reach a 50% chance of losing a bag (.99979^x = 0.5). Suffice to say most of us won't be losing a bag any time soon.

Two additional points on outlier cases...

1. Check the tags. Once, leaving a bicycle at the "oversized bag" ramp, a smart operator asked me why the bike's tag said "PHX" while the panniers said "PDX". A quick trip back to the checkin desk sorted that out. Doesn't happen often, but worth checking.
2. Don't pack anything that might be even remotely startling to The Authorities. Returning from Phoenix, AZ (PHX) one suitcase contained a tourist memento of a particularly American pastime - a folded but slightly holed sheet of paper with an outline of a human torso. That suitcase was inexplicably missing on arrival, but turned up a day or so later. I can only guess the image appeared faintly on X-ray, and somebody decided they wanted to look at it. I am probably on file somewhere, but at least the airline paid for delivery to my home.

Options:

• Don't check your luggage through to your final destination. This means at the transit point(s) you will need to:

  • collect your baggage from the baggage claim
  • go through customs and immigration
  • check your baggage to the final destination
  • return through security and immigration.

• Don't worry about it. Take a spare pair of pants, and perhaps a tee-shirt in your carry-on luggage, and just wait for the airline to deliver you baggage to you.

The first option is much simpler if you can arrange to spend a couple of days at your transit point.

A direct flight may reduce the likelihood of your luggage not being there when you arrive, but it won't eliminate it. I've taken direct flights only to find out that my luggage was not put on the same plane. The plane had reached capacity before all the luggage could be loaded (at least that was their explanation), so they sent my luggage along with a later flight. That's happened twice, and the delay ranged from a couple hours to a couple days.

Fortunately for me, it was always on my journey home, and all I had to do was wait until they delivered the missing luggage to my home. It would have been a lot more inconvenient if it had been at my destination.

In fact, I believe I've never had an issue with luggage on trips that required transferring.