Which level are you taking? I passed N2 with reading as my highest score. These are my methods so take all advice with a grain of salt!
If you can read more! Choose books where you know most of the words but need to check a few (I usually aim to pick books where there is only 1-3 words on the first page I don’t know) Or if you’re working on speed, choose children’s books.
Another way is to watch shows in Japanese with the Japanese subtitles on. You can get used to hearing natural grammar flow/ increase reading speed this way. It also helps you to get used to natural pacing in reading. For hard mode, mute the sound and do your best!
Another way I practice reading is to practice comprehension. If you’re lower level, choosing things with an English translation available may help you. I practice comprehension by attempting to summarize and/or translate short articles or exerts by myself, checking by either looking at an available English translation or asking a tutor (italki)/ volunteer (hellotalk).
I think reading a lot is the best method of the three. Try not to get hung up on every detail, read as though you are a kid again pushing through your native language. Only looking up words if they appear often. Don’t be embarrassed or ashamed to read children’s books and work your way up.
You got this!! I’m rooting for you 