With titles there are a few things to keep in mind. A title need to be enticing to click on, but you need to keep the promises in your title realistic as well (aka, not clickbait). To build an example; say you shot a vlog at the zoo. Your first instinct might be to write a descriptive title, such as:
"Trip to the London Zoo"
However, this is not enticing to click on. Instead of describing the content generally, choose a specific event or feeling that you experience in the vlog, such as:
"Visiting my favorite animal in London zoo!" or "Feeding penguins in London Zoo!"
However, be careful here, as this is where you can fall into the 'clickbait realm'. Only describe things that you actually deliver on in the video.
"Almost getting eaten by a crocodile?!?!" might sound exciting, but if you just merely look at crocodiles in your vlog you have lured the viewer in under false pretenses (aka, clickbaiting).
Notice as well that I put everything in the present tense. If you put your title in the past tense, it signals that things have already happened and there's no rush to go and see it. Putting it in the present tense makes people feel like something is happening now, in the present time. Also keep your titles simple. Don't make your titles 25 words long and keep in mind that Youtube only shows the first 3 to 6 words (depending on mobile or desktop) of a title. Those words need to count, so if you're doing a series, always put the name of the series at the end.
Another thing you can do is 'strategic capitalization'. Putting your title in all caps might seem like a good idea to get noticed, but you're essentially just shouting at your audience. Instead, capitalize the words you really find important and would interest people the most. Back to our previous examples:
"Visiting my FAVORITE ANIMAL in London ZOO!" or "FEEDING PENGUINS in London ZOO!"
This way you are emphasizing what is going on in your video and leave people to wonder: 'What is your favorite animal?'.
And lastly, the thing most people here would tell you, is use searchable keywords. You can use Google Trends to compare words on their search-ability. You can tune it to where your target audience lives or put it to worldwide and in the second drop down menu you can actually search on Youtube searches. For example, in the title "Visiting my favorite animal", would it be better to use favorite or favourite? If you have a lot of US audience, favorite seems logical, but if you have a UK audience you might want to use favourite. Google trends can help you out here.
So this is worldwide focused on Youtube search. Favourite had a peak last february, but overal most people are searching for favorite. However, you can look more specific as well, comparing 'favourite animal' and 'favorite animal'.
You can see this is much closer, with 'favourite animal' occasionally beating 'favorite animal', but favorite still seems the way to go.
So this was a very long answer to a seemingly easy question. I hope this clears things up for you!
(credits to Draw with Jazza's Skillshare course for some of this information!)