A lot of beginners make mistakes in how they play the ukulele, or rather, how they learn to play it. The biggest mistakes are made by those who switch from guitar. The first thing to remember is that the ukulele is not a guitar :-). So it is played in a slightly different way. I’m thinking mainly of strumming the strings. Not holding chords.
Where the buzz is
On guitar you play through the sound hole (mostly), but on ukulele you strum roughly where the body ends and the neck continues. Squeeze a chord and try it out for yourself, that’s where it sounds best. The more proficient a musician you become, you’ll find that sometimes it’s good to change that wrist position when playing a song to achieve interesting sound effects in the song, but as a beginner it’s good to get used to this way.
What to strum with and hand position
Proper ukulele players strum with their index finger, so forget the guitar pick. You’re learning the ukulele. Since the position and method of strumming is difficult to describe, it’s better to watch a 2 minute video. It’s in English. If you don’t know English, that’s okay. Watch carefully and you’ll understand for yourself. In the first half you will learn the basic rhythm, in the second half of the video you will see it in slow and detailed version :).
Czech YouTuber Guitarontheway shows you more in his video.
Correct strumming technique
When you are sitting, you should rest the ukulele on your thigh and apply light forearm pressure from above. I mean, more like resting it lightly on your forearm. When playing, use only your wrist. Don’t swing your whole arm, because it’s exhausting and your arm will soon tire.
Ukulele course and playing school
A self-taught beginner on his first instrument always has it a little harder, because he has to deal with many problems that he cannot find answers to. I’ve been through it myself. I didn’t know how and when to change chords, what rhythm to choose, how to find the right rhythm for a song, how to hold chords correctly. I was looking for a ukulele course at the time, but there was nothing available. Today there are. It’s actually a kind of school of ukulele playing. If you want to know more, come read more about learning how to play the ukulele.