So, what is the best way to go about this, in my experience I would start by determining the nature of your trip and the equipment you will need for that climate, country, shoot, duration and goal. Also what are you doing when you arrive, are you hiking, walking or traveling further? If so you will want to explore ways to weight save. However if you have a fixed base like a hotel when you arrive, you have greater flexibility with what you can take and store safely. Be sensible with your choices, if you are traveling for a street photography shoot for example I wouldn't expect you will be adding a 600mm lens in your kit list, minimising what you ultimately travel with is key in keeping weight down and unneeded stress, but equally don't neglect equipment you will need.
Step 1: Lay it all out
A very simple way to cut down on equipment, organise your bag and ensure you have the right tools for the job. Think, do you have enough focal range in your lenses for what you are needing to do, could you do with out a 105mm prime lens when you are also taking a 70-200mm? Is there enough risk to your equipment to warrant a second body? Do you need all your filters or can you do research to determine a selective range you may need? Make sure you also layout things such as boarding passes, passport, tickets, hotel bookings, insurance documents and currency in order to allocate packing space for these as well.
Step 2: Carry on, or hold?
When traveling with equipment, I like to use my main photography bag (Manfrotto Bumblebee 220PL) as my main carry on bag. This will have all things of value to me inside both in terms of money and the photography trip in hand, this is because if my hold luggage is lost I would still be able to function when I arrive to do the shoot in some capacity. In this trip's case it consists of all lenses, main body, MacBook pro and charger, card reader, memory cards, spare camera batteries, external hard drive, Pluto smart trigger and external power bank. It also will have all documents and currency on board, as well as cleaning equipment and a first aid kit. Allow yourself extra time to go through security as they often like to scrutinise camera bags and equipment.
**Make sure you check carry on baggage allowances on your airline, and remember spare lithium batteries must be carried in hand luggage (maximum of 2), and every piece of electrical equipment needs to be charged in order to prove it works if asked or you risk losing it! Don't bother carrying spare alkaline batteries for things like speed lights if you can avoid it, put fresh batteries in everything before you go, and buy more when there if required.**
Hold luggage, this can be a pain and expensive if you get it wrong. If you are going for a long duration and traveling with a lot of supplementary kit it would be advised to pre-purchase extra allowance and allow yourself a cushion. For my four day trip to Krakow I opted for 20kg allowance, despite having less than 8kg of clothes. This is because I am taking my heavy tripod in the case as well as a box of other equipment. More on the box, this is a clear plastic box about a 1/3 of the size of my case which contains more miscellaneous things like chargers, speed lights, filters, crystal ball, spare camera, remote trigger, flash diffusers, charging bank and tripod tools. I fill the box, and place tea towels over the top then compress with the lid and use two thumb release straps wrapped around to keep it closed and things in place. Then clearly label it as photography equipment with my name, contact details and address. This is the best way I have found to transport equipment in the hold to give it protection and transparency incase searched, it can be removed in one go and inspected without being opened or disrupting the rest of the case.
Tips and tricks:
1. Get yourself a charging bank - In my box I carry a charging bank, it is the bulkiest item I carry in there, but it has 6 usb ports and 3 standard english 3 pin plug ports for charging. This means you will only need 1 adapter for the country you are traveling to to charge all your equipment over night, and will save you rooting around the hotel room for plug sockets, unplugging tv's and lamps to get everything on charge.
2. Silica gel sachets - When ever you buy something which arrives with silica gel sachets inside keep them! Scattering them inside your main bag and the travel box will make sure moisture is kept to a minimum, especially with temperature changes and the risk of condensation.
3. Have all your documents in a plastic wallet inside your photography bag - This is just a standard rule of thumb for any abroad travel, have all the documents together, in order and accessible at all times to make sure you aren't unpacking half your bag in the airport to find passports or boarding passes.
4. Check return flight allowances - If you are using a different airline to return make sure the allowances match up as when you went out, otherwise you could risk further charges or needing to mail equipment home.... definitely not recommendable.
5. Research - Get research done prior to the trip, get and idea of what you will need and definitely not need, what is the weather like? Will you need water proof covers for your bag etc?
6. On the subject of water proof covers - If your bag comes with a water proof cover I highly recommend you have it on all the time when abroad in an unknown location, it adds an extra layer of security to your bag and equipment, as well as important documents you have in there.
7. Create a photography ID badge - Creating a photography ID badge with your name, contact details, a photo of yourself and a QR code to your website can be an easy way of gaining the trust of people who may not speak your language, or help put people's mind at rest when they see you with a big camera or they question what you are doing. Be open and friendly.
8. Laws - Research the laws regarding photographing certain subjects in other countries and know your rights as a photographer, you may infringe on some legislations which would be fine in your home country.
9. Cheat Sheet - If you are going to a country which you do not speak the native language create a cheat sheet which has some sentences which could come in useful in their native language. For example, "Hello my name is Tom Nixon, I am a photographer from the UK, is it okay if I photograph you and what you are doing."
10. Do the clear box trick for hold luggage equipment transport - It also gives you a good storage facility for unneeded equipment at the hotel to keep organised.