Hitchhiking in Ukraine is not the most popular way to get around the country but still it’s pretty acceptable and usualy you can get around quite easily by hitchhinking.
Ukrainian drivers are used to hitchhikers because many locals also do it. Bear in mind that quite often drivers expect a small payment which is generally discussed until you sit into the car. However no driver will be as pushy as those in some of Middle East or Asian countries. They will be more curious in foreign guest than offensive.
Language barrier might be a small concern becase not many people speak English. However if you know a few words in any of Slavic languages (eg. Polish, Chech, Serbian) basic communication won’t be a problem. And Russian of course is widely spoken throught the country.
In order to stop the car or truck locals usually simply wave with a hand. So thumbing-up will show that you are a foreigner which might give you more chances to be picked-up on the crowded bus stop just outside the city.
It’s pretty easy to find a good spot for hitchhiking in Ukraine. Ukrainian cities are not very spread out. There are no huge intersections and long parts of highways which are hard to cross on foot. To get to a good spot simply use city public transport. Buses and marshutkas will get you right to the place where you need. Just outside the city towards the right direction for you.
Note that public transport in Ukraine (trains, buses) is very cheap comparing to other European countries. So if you main point of hitcking is to save money, probably there are other options to do it better. Like eating out, for example, accomodation or shopping.
Distances are also very long. E.g. Lviv-Kyiv 550 km, Kyiv-Odessa 450 km. So in worst scenarion you’ll might see the sunset on a petrol station. Night sleeper trains is great alternative for long rides and hitchhiking is great to get around short distances.