#1 Use EVE Gate Check and Zkillboard to check your route
First enter your route into EVE Gate Check to see if there has been any killboard activity in the past hour on your route. If there has been, then check the system(s) on Zkillboard to see who targeted what type of ships to get more intel.
Even if there hasn't been any recent activity, there are some systems that are commonly camped by gankers. These include the following: Uedama, Sivala, Juunigaishi, Anttiri, Balle, Gheth, Ohide, Bagodan etc. If these systems are on your route, it might be good to check them on Zkillboard and see when the gankers usually are active and transport your stuff during times when they aren't. Note: trade hubs like Jita and Amarr are usually camped as well, use docking and instaundocking bookmarks to avoid being ganked there.
Another useful intel channel is UedamaScout. He live streams the character lists of multiple ganking hotspots. Check out UedamaScout on Twitch.
#2 Scout the system before jumping
If you are worried there might be gankers in a system, scout it before jumping in. Just dock your ship with valuables in a station in the previous system, grab a corvette and jump into the potentially camped system. See who is online in local chat, and if there are any ships on the gate. Alternatively, if you have a friend or two omega accounts, use one ship to go into the system before the ship with the valuables to see what's on the gate.
Ships commonly used for ganking are: Catalyst, Coercer, Thrasher, Vexor, Rupture, Tornado, Talos, Oracle, Purifier. If you see these ships on a gate, then it might be dangerous to enter the system.
Alliances that typically engage in highsec ganking are: Safety., Safety. Net, Novus Ordo., CODE., Goonswarm Federation, R.E.M.N.A.N.T.S and many more. It might be worth it to add these groups as red in your personal contacts so that you see them in local chat when you travel through systems.
#3 Microwarp cloak trick
This requires an omega account and some skill, but if you find yourself on a gate with multiple ganking ships, you can use the microwarp cloak trick to get away. Basically you equip an Improved Cloaking Device and an appropriately sized microwarpdrive on your ship (50MN for haulers, 500MN for Orca and other big ships), this works for both transport ships (some haulers, DST, Orca) and big slow ships like battleships.
When you enter the system, you align to the out gate and activate your microwarpdrive and cloaking device. Once the microwarpdrive cycle nears its end, you deactivate the cloak and press warp, and your ship should warp off instantly. This requires some practice to get it right, but it can save your butt in a lot of situations.
#4 Tank your ship for transport
If you are moving some valuable cargo that is not big in size or equipped to your ship, consider adding more passive tank on your ship like shield extenders, armor plates or reinforced bulkheads. Then you can also put on a damage control and shield or armor hardeners, both passive and active modules can be used. But if you have active mods, remember to activate them when needed.
Transport ships that have more capability to be tanky include: Nereus, Sigil, Wreathe, Badger, Deep Space Transport (DST) ships. You could also use a naturally super tanky ship like a freighter to move your items, and add reinforced bulkheads to the low slots for even more tank. To tank one hit from a Tornado, you need over 12000 EHP.
#5 Use courier services to transport your valuables
You can also outsource the risk to professional courier services. This will cost you ISK in terms of a transport fee. But if the ship and cargo are destroyed in transit, you will be refunded in ISK as per the collateral you have assigned to the contract.
There are two popular transport services called Red Frog Freight and PushX. They are reliable and reasonably priced.